Conseil Scientifique et Technique du SPhN

RESEARCH PROPOSAL

Title: The AGATA project – High-resolution Gamma-ray Spectroscopy of Exotic Nuclei

Experiment carried out at: Legnaro, GANIL/SPIRAL2, GSI/FAIR

Spokes person(s): Wolfram KORTEN (2007-09)

Contact person at SPhN: Wolfram KORTEN (Wolfram.KORTEN@cea.fr)

Experimental team at SPhN: A. Görgen, W. Korten, A. Obertelli, B. Sulignano, Ch. Theisen,

Theoretical support: T. Duguet (SPhN) and DIF/DPTA/SPN (Bruyères-le-Châtel)

List of DAPNIA divisions and number of people involved: SEDI, SIS

List of the laboratories and/or universities in the collaboration and number of people involved:

AGATA collaboration (see attached annex A of the new AGATA MoU)

SCHEDULE

Possible starting date of the project and preparation time [months]:

experimental programme with the AGATA Demonstrator at LNL from summer 2009

REQUESTED BUDGET

Total investment costs for the collaboration: 12440 k€

Share of the total investment costs for SPhN: 820 k€ (2009-2012)

Investment/year for SPhN: 205 k€

Total travel budget for SPhN: 120k (2009-2012)

Travel budget/year for SPhN: 30k (technical missions only, research missions from physics budget)

If already evaluated by another Scientific Committee:

If approved Allocated beam time: Possible starting date:

If Conditionally Approved, Differed or Rejected please provide detailed information:

The AGATA project High-resolution gamma-ray spectroscopy of exotic nuclei

Introduction AGATA, the Advanced Gamma Tracking Array, is the next generation high-resolution gamma-ray spectrometer facility for nuclear structure studies based on the novel technique of gamma-ray tracking. Since 2002, the European Gamma-ray community has launched a joint effort to pursue a Research and Development programme which allowed developing all elements of this new spectrometer and to evaluate their performance. In addition, the first implementation of the array, the AGATA Demonstrator, consisting of 5 AGATA modules, has been constructed. It is currently being assembled at the Legnaro National Laboratory (LNL), Italy and will be operational from 2009. The investment for the Demonstrator (~6M€) comes essentially from Germany, France, Italy, Sweden, Turkey and the UK. As the next step the collaboration is planning to build and operate 20 AGATA modules, i.e. 1/3 of the full array by 2012. A new Memorandum of Understanding (MoU) for the construction and operation of AGATA has been recently completed and was signed by the first partners. It is hoped that the French partners in AGATA (CEA/DSM and CNRS/IN2P3) will soon adhere to this MoU once the different scientific committees have evaluated and endorsed the project to the respective directions. The CSTS of SPhN is the first of these committees to evaluate the proposal for the construction of AGATA. In the first part of this document a brief summary of those aspects of the AGATA physics case is given where the SPhN nuclear structure group has a particular interest. The second part deals with the technical description of the proposal, while the third part describes in more detail the planned SPhN physics programme with AGATA in the next 4-5 years. Finally, we summarise the request for finances and human resources needed to pursue the project. 1 High resolution spectroscopy programme at SPhN (2009-2012) High-resolution gamma-ray spectroscopy is an essential tool of the nuclear structure group at SPhN to pursue its physics goals in the domain of nuclear shapes and shape coexistence, the evolution of shell structure and for the study of transfermium elements. Here we summarise our intentions for the scientific programme with AGATA in the near and mid-term future until the new facilities SPIRAL2 and FAIR will come into operation. The principal aspects of our current research programme concern the shell structure of nuclei, both in very heavy elements and when approaching to the drip-lines, and the development of nuclear shapes. Both topics are in fact very closely related: While the “classical” shell structure is responsible for an enhanced stability of spherical nuclei, the development of different nuclear shapes and their coexistence in the same isotope is a consequence of how the shell structure evolves as function of the degree of deformation. In addition, varying the neutron-to-proton ratio has important consequences on the shell structure. In order to enhance this effect our studies are mostly performed in nuclei far from stability, i.e. at the top of the nuclear chart in the transfermium elements, close to the proton drip-line, and as far as possible in the territory of neutron-rich isotopes.

1.1 Spectroscopy of Transfermium elements This part of our programme was started about 10 years ago at the University of Jyväskylä with the in-beam spectroscopy of the first transfermium isotope, namely 254No. Today, we are particularly interested in the spectroscopy of odd-mass Transfermium isotopes, which can give insights into the position of the single-particle orbitals responsible for the unknown and heavily disputed shell closures beyond 208Pb. The spectroscopy of two quasi-particle states in even-even nuclei also presents a stringent test for nuclear structure models. Besides our continuing engagement in Jyväskylä, we are also planning to perform specific experiments at GANIL using the AGATA and the VAMOS spectrometers. In order to learn more about the single-particle structure of transfermium nuclei and about the stability of superheavy elements, it is important to extend the spectroscopy of the heaviest elements in two directions:

• spectroscopy of 1qp-states in odd-mass nuclei and 2 qp-states in even-even nuclei, • spectroscopy of “less neutron deficient” isotopes produced with heavy targets such as

238U (“hot fusion” reactions) .

Figure 1.1 : (a) Spectrum of singles γ rays assigned to 255Lr (in delayed coincidence with fusion-evaporation residues). (b) Sum of γ -ray spectra projected from the recoil-gated γ γ coincidence matrix in coincidence with transitions marked by dashed lines.

Figure 1.1 shows the current state-of-the-art for the spectroscopy of odd-mass transfermium nuclei using the Jurosphere gamma-spectrometer and the RITU gas-filled separator at JYFL. The different rotational bands observed in the deformed nucleus 255Lr can only be assigned partially, due to a clear lack of γγ coincidence data. The coupling of AGATA with VAMOS, already in a 1π configuration, provides opportunities to significantly improve the spectroscopy of transfermium elements. VAMOS is particularly well suited for very asymmetric nuclear reactions, such as Oxygen or Neon on Uranium targets, which cannot be performed at any other place. These reactions lead to neutron-rich reaction products that are not accessible using heavier ions. As a consequence of the low recoil energy of the reaction products only a spectrometer with a very large-solid angle allows to detect the reaction products with sufficient efficiency of around 40% for such reactions.

A first experiment of this type to study 255No has been accepted by the GANIL PAC. In order to improve the focal plane detection of VAMOS and in particular to apply to Recoil Decay Tagging technique, we are developing a new focal plan detection system (MUSETT), which has been discussed at previous CSTS meetings and is financed by the French ANR. Beam time will be requested at the next Ganil PAC to perform the first MUSETT in-beam commissioning. An efficiency of about 30% is expected for the 1π Agata array in the energy range of interest. In this way we will be able to measure and exploit gamma-gamma coincidences with a much higher probability than any other array currently in use. Adding the larger counting rate capabilities of about 50 kHz per crystal, we can expect an overall gain in sensitivity of at least two orders of magnitude for coincidence measurements. In this way the much more complex spectra of odd-mass nuclei can be resolved, probably up to Z=104. For singles measurements we may be able to reach a sensitivity of a few tens of nb allowing to further go up the nuclear chart towards the deformed magic nuclei around Z=108. Reaching them will nevertheless require the full AGATA array. In the long term, the radioactive beams from SPIRAL 2 provide a unique opportunity to reach the deformed island of stability around 270Hs. Symmetric reactions using neutron-rich beams of Xe or Kr are promising, although detailed reaction mechanism studies are a mandatory prerequisite. Details of this long-term program have been developed in a SPIRAL2 LoI «From actinides to superheavy elements with SPIRAL 2: reaction dynamics and structure ». 1.2 Shape coexistence in exotic nuclei Our experiments investigating the shape coexistence phenomenon in nuclei around the N=Z line at mass A=70 have shown the potential of Coulomb excitation measurements using low-energy radioactive ion beams employing highly efficient gamma arrays, such as EXOGAM or Miniball. The experiments performed with 76Kr and 74Kr beams from SPIRAL were the first reorientation measurements using radioactive ion beams and allowed a coherent description of the shape coexistence in these nuclei. Our recent Coulomb excitation experiment with an 44Ar beam showed that static quadrupole moments can also be extracted for non-collective, almost spherical nuclei close to the shell closures. Future key experiments of this kind would be the study of the N=Z nuclei 72Kr and 68Se as well as the development of shell closures at N=28 and N=40, but the feasibility of these experiments will require an intensity upgrade of SPIRAL beams by a factor of 5-10. In our experiments we have also shown that a combination of Coulomb excitation of radioactive ions and lifetime measurements of nuclei produced by stable heavy-ion beam induced reactions are very complementary means to study shape evolution and coexistence. In the future we are planning to focus the lifetime measurements on moderately neutron rich nuclei produced in multi-nucleon transfer and deep-inelastic reactions. More details on this programme are given in sections 3.1 and 3.2 Finally, we plan to extend our investigations of shape evolution using two-nucleon transfer reactions with intermediate-energy beams around 40-50 MeV/nucleon. A first (p,t) experiment in the light Se isotopes has been accepted at GANIL in 2007 to characterise the method. Due to the current unavailability of SISSI, this program is currently pending. However, we plan to continue this program with Kr and Ge isotopes to characterise the nuclear shapes, and more generally the underlying two-body correlations.

Figure 1.2 : Coulomb excitation spectra of 76Kr (left) and 74Kr (right) obtained with the EXOGAM spectrometer at GANIL and showing the current state-of-the-art in gamma-ray spectroscopy using low-energy radioactive beams.

All these future experiments will strongly profit from AGATA mainly due to the enhanced position sensitivity and the higher count-rate capability. The position sensitivity will be most important for the high-energy reactions, but the low-energy Coulomb excitation measurements also show already some limitations due to insufficient energy resolution (see figure 1.2). In these Coulomb excitation experiments the gamma spectrometers are coupled to highly segmented silicon detectors for the detection of scattered particles. We are taking advantage of synergies with the MUSETT project by developing a highly integrated ASIC electronics for these Si detectors, which will allow a higher segmentation and therefore better angular resolution. In this way we will be able to fully exploit the better angular resolution obtained by using digital pulse processing of the Germanium detectors. The higher count rate capability will be primordial when using high-intensity radioactive ion beams from SPIRAL2. In our 44Ar Coulomb excitation experiment we were already encountering the limiting factor of high background radiation from the relatively intense beam (106 pps), which will be lifted when using AGATA. 1.3 Shell structure changes in nuclear far from stability This part of our scientific programme is still in an early stage of development. We plan to use inelastic scattering and nucleon removal on proton targets to complement the Coulomb excitation and nucleon pickup experiments, respectively. Indeed, combining the results obtained by Coulomb excitation and inelastic proton scattering will allow extracting the proton and neutron transition probabilities independently. The ratio of the two transition probabilities is directly comparable to theoretical Mn/Mp ratio and allows to investigate a possible decoupling of neutron and proton deformations. Nucleon-removal reactions at intermediate reactions are effective probes to study hole states in very exotic nuclei, very complementary to nucleon-pickup reactions that populate single-particle states. Using proton scattering to populate excited states in very exotic species has several advantages. Relatively thick targets can be used for (p,p’) reactions if the excited states are measured by gamma-ray spectroscopy. Using a pure (solid) hydrogen (or later deuterium) target further increases the number of target atoms for a given energy loss of the beam in the target. Even though the reaction cross sections are lower than for electro-magnetic excitation

in heavy targets the total reaction rate will be higher. This allows accessing more exotic nuclei which are produced with a lower rates as low as a few particles per second. We are currently investigating possible candidates for a first experimental proposal both at SPIRAL energies, but also fragmentation experiments at GSI, with a particular emphasis on shell closures in neutron-rich nuclei, e.g. at N=40. The expertise of IRFU/SACM in developing liquid H2 targets will strongly benefit these experiments. Gamma-ray spectroscopy of low-energy transfer reactions is also investigated as a tool to further understand the underlying single-particle shell structure and the evolution of shell gaps. A first experiment using gamma-rays as probe of states excited in a (d,p) reaction was successfully performed at GANIL to measure excited states in 27Ne. These experiments will strongly profit from the AGATA array, in particular those performed at intermediate or relativistic energies where the Doppler effects are much more important. Current Ge detector arrays with limited spatial resolution, e.g.. the Euroball Cluster detectors employed for RISING, are severely limited in this domain (see section 3.3), while the alternative use of scintillation detectors has its limitations due to the poor energy resolution. 1.4 Conclusions The experimental programme described above relies on the construction of a more powerful gamma-ray spectrometer, which improves on the several aspects beyond the current state-of-the-art. First an ever higher detection efficiency is needed coming as close as possible to 100% at least for low-energy gamma-rays. At the same time the energy resolution must not exceed a few keV under real experimental conditions, that is for emitting nuclei travelling at a speed as high as 50% of the speed of light. Furthermore, the spectrum quality measured as peak to background ratio for single gamma-rays must stay above 50% in order to effectively exploit gamma-gamma coincidences. Finally, the future experiments will be performed in more hostile environments often with a huge background of unwanted gamma-rays, e.g. from the radioactive decay of the beam particles. Optimising all these parameters simultaneously requires building a complete 4π shell of Germanium detectors and a radical new concept in dealing with the high scattering probability of gamma rays (within and between the detectors) until the full energy has been released and absorbed by the Germanium detectors. This new concept known as gamma-ray tracking can be achieved by using position-sensitive Germanium detectors and “disentangling the path” of the gamma-rays from the individual interactions. Having all the properties described above, the Advanced Gamma Tracking Array, AGATA, will allow for the first time to exploit gamma-gamma coincidence measurements on exotic nuclei which cannot be reached by the classical production methods using stable ions beams. Therefore we believe that AGATA will mark an equally important leap in high-resolution nuclear spectroscopy as it was the case in the early 1980s with the construction of the first “large” Germanium detector arrays.

2 Technical proposal for the construction of AGATA AGATA is the next generation high-resolution gamma-ray spectrometer facility for nuclear structure studies based on the principle of gamma-ray tracking. A gamma-ray tracking system involves accurately measuring the positions and energies of all the gamma-ray interaction points in the detector segments. The position of the first interaction defines the angle of emission of the gamma ray from the source (the site of the reaction), relative to the detector, which is particularly important when detecting radiation emitted by recoiling product nuclei since it determines the extent of the gamma-ray energy spread arising from the Doppler shift. The angular definition in AGATA, compared with current systems, will result in an order of magnitude improvement in spectral response. Since most of the gamma rays interact more than once within the crystal, the energy and angle relationship of the Compton-scattering formula will be used to track the path of a given gamma ray. The full energy can then be reconstructed by summing all the individual energies deposited for a particular gamma ray. Very high efficiency can then be obtained in a 4π tracking spectrometer since there are minimal dead areas. The realisation of such a system requires the development of highly-segmented germanium detectors, digital electronics, pulse-shape analysis to extract energy, time and position information, and tracking algorithms to reconstruct the full interaction (see figure 2.1).

The milestones which were achieved during the research and development phase of AGATA are listed below.

4

• Development of a highly-segmented encapsulated Ge detector • Development of a cryostat to hold a cluster of segmented detectors • Design and development of digital electronics • Development of algorithms for energy, time and position determination

Pulse Shape Analysisto decompose

recorded waves

Highly segmented HPGe detectors

· ·

··

Identified interaction

points(x,y,z,E,t)i

Reconstruction of tracks e.g. by evaluation of

permutations of interaction points

EγEγ1

Eγ2

e2

e3

1

3

θ1

θ2

e1

0 2

Digital electronicsto record and

process segment signals

γ

1

2 3

reconstructed γ-rays

41

Identified interaction

points

Reconstruction of tracks e.g. by evaluation of

permutations of interaction points

Highly segmented HPGe detectors

(x,y,z,E,t)i

· ·

··

Pulse Shape Analysisto decompose

recorded waves Eγ

Eγ1

Eγ2

e2

e3

1

3

θ1

θ2

e1

0 2

Digital electronicsto record and

process segment signals

γ

2 3

reconstructed γ-rays

Figure 2.1: Constituents and information flow of AGATA

• Development of tracking algorithms • Design and manufacture of associated infrastructure

During the last 6 years all elements for AGATA have been developed and their performance has been evaluated. As a last step the construction of the Demonstrator is currently under way, which will be followed by performance tests both with sources and in-beam. The AGATA management board is currently editing a full technical design report which will be completed by the end of this year. In the following a short summary of the design and the performance as well as the status of the different components is given. 2.1 Conceptual design and performance of AGATA The optimum performance or sensitivity of a gamma-ray spectrometer is obtained by maximising the full energy (photopeak) detection efficiency whilst maintaining the best spectrum quality. For AGATA these quantities have to be maximised for both low and high multiplicity and low and high velocities (up to v/c ~0.5). In addition AGATA must (i) have very good angular resolution to determine the emission direction of the detected gamma ray, (ii) be able to run at very high rates, either because of high radioactivity or high beam intensities, and (iii) have sufficient space around the reaction site to allow additional (ancillary) detectors to be installed. The AGATA collaboration has investigated several options for the design of the spectrometer. Several geometries with different numbers of detectors have been considered, tiling a sphere with various numbers of hexagons and 12 pentagons. The performance of AGATA has been simulated using a Monte Carlo code based on GEANT4 which calculates the interaction of gamma rays in the detectors, and allows inclusion of realistic shapes and passive materials.

The geometry that has been chosen is based on tiling the sphere with 180 irregular hexagons with 3 slightly different shapes and 12 pentagons as shown schematically in Fig. 2.2. In this geometry the 180 hexagons can be grouped into 60 identical triple clusters. The remaining pentagonal gaps will be used for supporting the array and access to the inner region (the target chamber). Table 2.1 summarises the characteristics of the 180-detector geometry and Table 2.2 gives the calculated photopeak efficiency and peak-to-total at 1 MeV for various multiplicities. It should be noted that the performance of a gamma-ray tracking array depends strongly on the pulse-shape analysis and gamma-ray tracking algorithms, in particular for high multiplicities. The development and optimisation of these is a major part of the AGATA project and it is expected that the given performance

figures will further improve. Nevertheless, Table 1.2 shows that the 180-detector spectrometer will have a very high efficiency and excellent spectral response even with high gamma-ray multiplicities. This geometry has a high granularity with an angular resolution of 1.25○ which is very important for Doppler corrections at high recoil velocities.

Figure 2.2 180-detector geometry of AGATA. The colours (red, green and blue) indicate the slightly different shapes.

Number of crystal shapes 3 Number of cluster shapes 1 Number of clusters 60 Solid angle coverage 82% Amount of Ge 363 kg Target-to-crystal distance 23.1cmNumber of electronics channels

6660

Table 2.1 Characteristics of the 180-detector AGATA spectrometer.

Multiplicity 1 10 20 30 Full-energy efficiency (%)

43.3 33.9 30.5 28.1

Peak-to-total ratio (%)

58.2 52.9 50.9 49.1

Table 2.2 The predicted performance of the 180-detector AGATA spectrometer for 1-MeV gamma rays.

2.2 Germanium detectors and infrastructure

The gamma-ray detectors of AGATA use 36-fold segmented coaxial high-purity germanium (HPGe) crystals. The crystals have a length of 9 cm and an initial diameter (before shaping) of 8 cm. In order to fit into the 4π geometry, the cylindrical crystals are tapered to a hexagonal shape at the front of the crystal with an ~8○ tapering angle. A schematic representation of the capsule is shown in Fig. 2.3. In the 180-detector configuration, three slightly different shapes are required to maximize the solid-

angle coverage. Each crystal is encapsulated into a thin aluminium can using the same technology that was developed for the EUROBALL Cluster and the MINIBALL detectors. The outer contact of each crystal is divided into 6 6 azimuthal and longitudinal segments to give 36 electronically independent outputs. The HPGe detectors for AGATA are produced by Canberra in their French factory in Lingolsheim.

Figure 2.3 Schematic representationof an AGATA detector capsule.

The 15 asymmetric capsules ordered by the AGATA collaboration for the Demonstrator have the geometry of the 180-detector configuration with an 8○ tapering angle. The longitudinal segmentation scheme has segments in steps at 8, 13, 15, 18, 18, and 18 mm from the front of the crystal, which has been optimised to equilibrate the effective size of the segments as determined by the electric field lines. The AGATA collaboration has developed, in conjunction with the German company CTT, cryostats for single capsules, and has designed and commissioned specialised preamplifiers for the capsules (Cologne core preamplifier, Milano and GANIL segment preamplifier) which have the necessary fast rise times and high bandwidth. Specification parameters for the AGATA capsules are listed below.

• All 36 outer contacts with energy resolution < 2.3keV at 1.33 MeV and < 1.3 keV at 122 keV

• Core energy resolution < 2.35 keV at 1.3MeV and < 1.35 keV at 122 keV, • Cross talk below 10-3.

The AGATA collaboration has negotiated an agreement with Canberra Eurysis such that customer acceptance tests can be performed by the collaboration using a specified set of equipment and test procedures. These acceptance tests are performed in two laboratories of the collaboration (U. Cologne, IKP and CEA Saclay, Irfu).

The AGATA detector module comprises of three capsules with slightly different asymmetric shapes mounted together in a triple cryostat to operate the detectors at liquid-nitrogen temperatures. These triple cryostats are developed by the company CTT in association with the AGATA collaboration. To date the first two modules were successfully assembled and tested and a third one is under construction; the two final modules for the Demonstrator are expected early in 2009. The design of the cryostat has to meet the tight mechanical specifications defined by the mechanical-design team in order that the cryostats fit exactly into the 4π geometry. The integration procedure is now well under control, but the transfer of competence from the cryostat manufacturer CTT to the collaboration still has to be achieved. Besides some technical difficulties in an early stage of the production and a certain number of rejected Ge detectors due to imperfections of the Ge crystals the delivery is going rather smooth. At the time of writing the collaboration has accepted 9 detectors out of 15 ordered. The remaining detectors had to undergo a revision and are expected to be redelivered by the end of this year. The timescale for delivery of detector capsules from Canberra Eurisys is currently one capsule every six-to-eight weeks which is taken into account in the project schedule. It is expected that the AGATA steering committee will soon start negotiating with Canberra the conditions of delivery for a series of 45 Ge detectors between 2009 and 2012. The AGATA Detector Support System (DSS) is developed in a collaboration between Irfu and GSI. It consists out of the low-voltage supplies for the preamplifiers and front-end electronics, the high-voltage supplies for the Ge detectors and the automatic LN2 filling system for the Ge detectors. Prototypes for all elements have been successfully tested and the first units are to be installed in Legnaro by the end of November. The system for 5 AGATA modules will be will completed by next spring. 2.3 AGATA electronics and data acquisition

AGATA requires a state-of-the-art, purpose-built digital electronics and the associated data-acquisition system to process the signals from the germanium detectors. The full system has to cope with over 6000 channels each with rates up to 50 kHz. A schematic diagram of the system architecture is shown in Fig. 2.3. The segmented detectors provide 37 signals (36 outer contacts, 1 core contact) from the FET/preamplifier. The principle of the AGATA electronics is to sample these outputs with fast ADCs to preserve the full signal information in a clean environment so that accurate energy, time, and

position can be extracted. The first stage of the electronics will be a digitiser card, located close to the detector. The digitiser contains 100-MHz 14-bit ADCs to digitise the signal before it is transmitted via an optical link to a "remote" pre-processing card. This card performs digital signal processing that is specific to a particular detector, such as energy

Figure 2.3: Block-diagram of the AGATA electronics and DAQ.

determination and time. These cards transmit their outputs to the pulse processing part of the system which will be a farm of computers. The farm assembles the full data from all elements of the array, uses pulse-shape analysis algorithms to determine the position of the interactions, performs tracking to reconstruct the events and assembles the resulting data for storage. The whole system shares a global time reference (clock), supplied by a global trigger and synchronisation control system, which is distributed by a network of optical fibres to the front-end electronics for each detector. The full chain of prototypes has been tested in summer 2008 and the full electronics for the AGATA Demonstrator is expected to be available in spring/summer 2009. 2.4 Pulse-shape and tracking algorithms and detector characterisation The performance of the gamma-ray tracking arrays will strongly depend on the capability of the pulse-shape and tracking algorithms. The task is not only to identify the individual interaction points of a gamma ray with an accuracy of a few millimetres and a low percentage of errors, but also to find algorithms which are fast enough for real-time application with the computing power available in the near future. Intense research is going on in this field and encouraging results have been reported. It is expected that the performance of tracking arrays will continually improve during the project due to refined algorithms and increased computing power. Most of this work is based on a few common procedures as outlined below. As a first step, a basis of the detector response has to be created - the pulse shapes of the signals as a function of the energy deposited at points defined by a regular grid inside the crystal are required. Any observed signal corresponding to multiple interactions in the crystal can be expressed as a linear combination of the basis signals, where the coefficients are the energies deposited. The best basis system would consist of the measured detector response for each crystal. However, the measurement of the full characterisation of one highly segmented detector is very time consuming. Therefore, the response of the detector has to be calculated. By solving the Poisson equation for the geometry of the detectors, the boundary conditions of the electric field can be obtained. The concept of a weighting field is used to calculate the transient charge signals. The charge-carrier trajectories and the signals are calculated from the electric field in the detector taking into account the mobility of the electrons and holes and the crystal orientation. Application of the Ramo theorem provides the charge recovery at the contacts. A computer code known as Multi Geometry Simulation (MGS) is used to calculate the detector response for AGATA. In order to trust the calculated signals and resulting number of interactions and their positions, each detector has to be characterised in detail. Characterisation involves determining the pulse shape at each position in the crystal, which in turn involves scanning each crystal using a collimated gamma-ray source and recording typical pulse shapes. The first two AGATA symmetric capsules have been scanned at the University of Liverpool using a 920-MBq 137Cs source. Scanning is performed by moving the source accurately over a well-defined grid and recording events in coincidence with scattered gammas detected in an additional detector. The procedure is very time consuming and scanning of one detector typically takes two months. Even more time consuming is the analysis and understanding of the huge data sets from these scans. To date, the only operational scanning system and expertise to analyse the AGATA data is at the University of Liverpool. This situation is causing a bottleneck in the AGATA project since the data from the symmetric and first asymmetric capsules is urgently required. The AGATA collaboration is therefore setting-up new scanning centres in CSNSM Orsay and GSI. All of these centres are required since it is not known, if the pulse shapes for each of the

three detector shapes will be the same. Differences are expected with the different crystal properties (impurities, high voltage) and the effect of annealing or in-beam neutron damage is yet to be investigated. It is expected that detailed scanning of capsules will continue well into this second phase of AGATA. Following the scanning procedure, the pulse shapes of the experimental data are compared with the calculated basis in order to determine the coordinates of the interaction points. A gamma ray will normally have a chain of interactions in the shell of germanium detectors (e.g. 3-4 at 1.3 MeV). There can be more than one interaction in one detector segment or/and the gamma ray can be scattered to another segment of the same crystal or to an adjacent detector, or even across the shell. Several fitting procedures have been developed in order to decompose the measured signals into the given basis signals, such as genetic algorithms, wavelet decomposition, and a matrix method, the latter being studied in a collaboration between CSNSM Orsay and Irfu. In the third step a tracking algorithm is applied in order to disentangle the coincident interaction points and to determine the total energy and the emission direction of those gamma rays that have been fully absorbed in the germanium shell. Mainly two types of tracking algorithms have been studied so far: back tracking and forward tracking. The back tracking algorithm starts with the reconstruction from the last interaction, which is a photoelectric interaction of a fully absorbed gamma ray. The energy deposited in this final photoelectric interaction is most probably in the energy range of ~ 100 - 250 keV, independent of the energy of the incident gamma ray. The forward tracking algorithm starts with the assignment of the coincident interaction points to clusters in a (θ, φ) space. This clustering of interaction points was found in Monte-Carlo calculations due to forward peaking of the Compton-scattering cross section and the decreasing mean free path of the gamma-ray photons with decreasing energy. It has been shown that back tracking can reconstruct events that are missing in forward tracking and vice versa. Therefore, a combination of both methods can increase the tracking efficiency. A third type of tracking algorithm which has been tested successfully is based on fuzzy logic.

The properties of the prototype AGATA triple cluster were studied in two in-beam experiments in 2004 and 2005. The position sensitivity of the detector was used to reduce the Doppler-broadened line width and to calculate the position resolution. The reaction chosen for the second of these experiments was d(48Ti,p)49Ti. The 100-MeV Ti beam was provided by the Cologne tandem accelerator. The recoil velocity of the 49Ti ions was v/c = 0.06-0.07. The emission angle of the protons was measured with a double-sided silicon strip detector, which was segmented into 32 rings on one side and into 64 sectors on the other side. Preliminary results achieved with a grid method developed in Padova are presented in Fig. 2.4. By

pulse-shape analysis the line width of the 1382-keV peak in 49Ti was reduced from 32 keV to 5.3 keV, corresponding to an overall position resolution of 4.7 mm.

1382 keV

PSA

Segment

Full crystal

1382 keV

PSA

Segment

Full crystal

Figure 2.4: The 1382-keV peak in 49Ti produced following the reaction d(48Ti, p)49Ti at 100 MeV. The 49Ti recoil velocity was v/c=0.06-0.07. The effect of using information from the full crystal (black), one segment (blue) and pulse-shape analysis (red) is shown.

2.5 Current and future implication of IRFU in the AGATA project After a somewhat delayed start into the AGATA project, Irfu has become a strong partner in the collaboration with important responsibilities, in particular concerning the Germanium detectors. At SEDI a germanium detector laboratory has been successfully implemented, where the AGATA detectors can be mounted in single or triple cryostats, tested and validated. Since summer 2008 AGATA capsules are regularly delivered by the manufacturer to Saclay, where the customer acceptance tests are being performed. From 2009 also the assembly of triple modules is envisaged. In view of the increasing number of detectors, Saclay will be an important site to assure the maintenance of the AGATA modules. Therefore, a permanent staffing of the detector laboratory at SEDI with one engineer and at least one technician is required for the foreseeable future. At the SIS large parts of the detector support system (DSS) for AGATA have been developed. This comprises the complete low-voltage supply system for the detector preamplifiers, and the front-end electronics, the HV power supplies which are integrated on the AGATA detectors and the automatic liquid-nitrogen filling system, including the control system. We envisage that SIS continues this task for the next phase, i.e. they will continue to build a system for 20 AGATA modules and assure its maintenance at the different sites where AGATA will be exploited. The physicist at SPhN have contributed to many different aspects of the project, starting from the simulation of the best longitudinal segmentation of the Ge detectors, developing and evaluating algorithms for the pulse-shape analysis up to the simulation of AGATA in different experimental situations. They are also strongly involved in the day-to-day work at the detector laboratory. Some of this work will also continue after the start of operation, e.g. the PSA codes will be further developed and the experiment simulations will have to be refined and combined with the other spectrometers which will be used in conjunction with AGATA (see section 3).

3 Physics campaigns with AGATA (2009-2012) In this section we briefly describe the physics campaigns planned with AGATA in the next 4 years, together with the implication and the interests of the physicists from SPhN. 3.1 AGATA at LNL The research and development phase of AGATA has constructed a sub-array called the Demonstrator, which will comprise of the detectors, electronics, acquisition system, and the associated infrastructure. From 2009, the Demonstrator will be located at the target position of the magnetic spectrometer PRISMA at Legnaro National Laboratory, Italy. Initially a series of in-beam commissioning experiments will be performed to establish that tracking can be

achieved to fulfil the objectives of the first phase of the project. The Demonstrator will then be used for a physics campaign for 12 months. As new detectors and associated electronics become available they will be added to the spectrometer thus continually improving its performance. At the start of this phase, the collaboration will have 5 asymmetric triple cryostats plus one symmetric triple cryostat (15+3 capsules). A computer-aided design image of the AGATA structure mounted on the support platform of PRISMA is shown in Figure 3.1. As can be seen the framework allows for up to 15 triple cryostats to be mounted, giving expansion space if more detectors become available.

Figure 3.1 CAD image of AGATA with 15 triple clusters at the target position of PRISMA.

While the ultimate goal is a full 4π array, already the first sub-array is a significant advance in its own right and will provide a large gain in sensitivity for a number of experiments aimed at the most exotic nuclei. The performance of the 5-module array depends critically on the distance from the target position. Indeed, given the lack of spherical symmetry it is sensible to place the detectors closer to the target than the reference “standard” distance of 23.5 cm (for the 180-detector 4π array). A target to detector distance of 13.5 cm is possible.

13.5 cm 23.5 cm Gamma-ray multiplicity 1 10 20 30 1 10 20 30 Efficiency (%) 6.7 5.4 4.8 4.3 2.9 2.6 2.3 2.2 Peak-to-Total 52.0 52.2 50.8 49.9 51.4 51.0 51.0 50.6 Recoil Velocity (v/c %) 0 5 10 50 0 5 10 50 Efficiency (%) 6.5 6.9 7.4 11.6 2.9 3.1 3.4 6.0 FWHM (keV) 2.0 2.1 2.4 8.0 2.0 2.1 2.1 4.4

Table 3.1 Simulated performance of the AGATA Demonstrator at two target-to-detector distances, 23.5 and 13.5 cm, for 1 MeV photons. The photopeak efficiencies and peak- to-total ratios are calculated for multiplicities of 1, 10, 20 and 30. The photopeak efficiencies and resolutions, (FWHM, keV) are calculated for recoil velocity velocities (v/c) of 0, 5, 10, and 50%.

The performance of the AGATA Demonstrator has been calculated by the Simulation Team. The photopeak efficiency, the peak-to-total ratio, and the resolution (FWHM) will depend strongly on the target-to-crystal distance for different reactions with different gamma-ray multiplicities and recoil velocities. Table 3.1 summarizes the performance characteristics for the two distances (13.5 cm and 23.5cm) for a range of gamma-ray multiplicities (ranging from 1 to 30) and recoil velocities (v/c, ranging from 0 to 50%). For single gamma-ray events (multiplicity 1) the detection efficiency of the Demonstrator varies from 2.9% at 23.5 cm to 6.7 % at 13.5 cm. In many of the first experiments at Legnaro, deep-inelastic reactions will be used with recoil velocities of v/c ≈ 0.1. Such a high recoil velocity with a traditional gamma-ray spectrometer (such as EUROBALL) would lead to large Doppler broadening and poor energy resolution of over 15 keV. With the AGATA Demonstrator, the energy resolution is reduced to just 2.4 keV.

Figure 3.2: Spectra from the pioneering RDDS lifetime measurement after multi-nucleon transfer reaction using the PRISMA−CLARA setup at Legnaro. In the future the CLARA germanium detector array will be replaced by the AGATA Demonstrator. A dedicated plunger device is under construction, making the setup ideally suited for RDDS measurements in neutron-rich nuclei.

The main focus of the physics campaign at LNL will be the study of moderately neutron-rich nuclei produced in multi-nucleon transfer and deep-inelastic reactions. PRISMA has demonstrated its excellent properties for these experiments in previous campaigns with the CLARA Ge detector array. In order to demonstrate the impact of the Demonstrator on the physics campaign at Legnaro a brief comparison with the existing gamma-ray spectrometer, CLARA, is made. The CLARA spectrometer consists of 25 Clover detectors, and it has been successfully used in a series of experiments using quasi-elastic and deep-inelastic reactions to study neutron rich nuclei. CLARA has an efficiency between 2.6 % and 3% and a FWHM of 0.8 to 1.0 % for product velocities β = 8 % to 10 %. At a target-to-detector distance of 13.5 cm, the AGATA Demonstrator will represent an increase by a factor of 3 or 4 in the γ-γ-PRISMA coincidence efficiency and a factor of 4 in sensitivity. Moreover, for lifetime measurements a further increase by at least a factor of 2 has to be considered since all detectors of the Demonstrator are located in the sensitive angular range compared with less than half of CLARA. As a consequence AGATA will allow the study of nuclei further from stability than could be achieved with CLARA, but also open the way for more detailed studies

such as lifetime measurement of excited states using the Recoil-Distance Doppler-Shift (RDDS) method (see figure 3.2). After participating into a demonstration experiment of this new technique at LNL, the Saclay group has further pioneered this method recently at GANIL, where the new AGATA plunger has been used for the first time to measure lifetimes in neutron iron isotopes 62,64Fe. Unlike for example intermediate-energy Coulomb excitation, the new method is not restricted to the transition strength of the first excited state only, and it is expected to find several new lifetimes also for higher-lying states. The Saclay group has submitted a letter of intent to measure lifetimes in neutron-rich Zn isotopes using the RDDS plunger setup with PRISMA and the AGATA Demonstrator. A formal proposal will be submitted to LNL early 2009. This measurement will be complementary to the recent low-energy Coulomb excitation experiment on the even-mass Zn isotopes at ISOLDE. In this experiment the transition probability B(E2;0+→2+) was determined for the even-mass isotopes between 74Zn and 80Zn from the measured integral Coulomb excitation cross section, but only under the assumption that the quadrupole moment is zero. An independent lifetime measurement with AGATA will allow to determine the B(E2) value without any assumption, and combining it with the result from Isolde will also allow to determine the quadrupole moment and thus the shape of these nuclei. 3.2 AGATA at GANIL Following the Legnaro campaign, it is planned that AGATA will move to the GANIL laboratory in France. In order to have sufficient time for the campaign at LNL, the installation at GANIL is not expected before late 2010, but this campaign also depends on the planning to construct the SPIRAL2 driver accelerator at GANIL. Once this planning is known the final decision can be taken, probably early in 2009. Alternatively, AGATA could first go to GSI. The GANIL facility offers a large variety of radioactive and stable beams, ranging from 6,8He to 238U, over a wide range of energies from a few MeV/u up to 100 MeV/u. This wide spectrum of beams and several other state-of-the-art spectrometers for gamma-ray and particle detection, such as EXOGAM and VAMOS, will be utilised in this campaign. Consequently, the physics programme of AGATA at GANIL will be much wider than at LNL. Coulomb excitation experiments of 72Kr and 46Ar are the top priority of the SPhN group, but require higher primary beam intensity for 78Kr and 48Ca., which is currently limiting the feasibility of these experiments. Furthermore, new beam species of elements other than noble gases should be developed. This involves the development of new target-ion-sources for SPIRAL. Even though such a development requires a considerable commitment of resources and manpower, we rank it a necessary evolution of the SPIRAL project towards SPIRAL2. New beam species for SPIRAL will not only broaden the physics program over the next years, but also provide a head start on necessary developments for SPIRAL2. In addition, multi-nucleon transfer reactions can be performed at GANIL in inverse kinematics, e.g. using a 238U beam, further increasing the range of neutron-rich nuclei that can be accessed experimentally. In a recent experiment at GANIL the SPhN group has shown that this method is competitive with intermediate-energy fragmentation experiments at MSU. Finally, we plan to use AGATA at GANIL for transfer and inelastic scattering experiments at intermediate-energies using the (new) SISSI device to study the structure and correlations in exotic nuclei.

Figure 3.3. Possible scenario for the installation of the AGATA Demonstrator coupled to the VAMOS spectrometer and EXOGAM detectors in hall G1 at GANIL.

The optimum arrangement for AGATA has been investigated and the general conclusion is that to satisfy the majority of the science cases AGATA should be mounted at the target position of the VAMOS recoil spectrometer and coupled to the existing EXOGAM gamma-ray detectors. Geant4 simulations have been performed in order to determine the optimum distance of AGATA from the target, and to decide how it will be coupled with EXOGAM. The main conclusions are that the Demonstrator should be placed rather close to the target in order to maximise the total efficiency and that this can be achieved without a severe loss in spectrum quality. The 5-module configuration of AGATA will have a photo-peak efficiency of ~8% depending on the specific reaction. Even though the efficiency is smaller than that of the (full) EXOGAM array, the improved energy resolution and peak-to-total ratio result in a superior overall spectrum quality (quantified as the resolving power). Experiments will also benefit from the higher rate capability with the AGATA Demonstrator. It should be noted that during the GANIL phase the number of AGATA detectors will continue to increase and the performance will improve accordingly. The design of the structure will take this into account. A conceptual design study of the installation of AGATA at GANIL and in particular the coupling with EXOGAM has been done. The latest layout is shown in the figure 3.3, where the AGATA detectors are shown around the incoming beam line. In this way up to 10 AGATA detectors could be mounted in the backward hemisphere, still leaving space for 8 EXOGAM detectors around 90° with respect to the beam axis. A possible movement of the

AGATA detectors along the beam line would allow optimising the distance of the detectors to the target for individual experiments. The coupling of VAMOS and EXOGAM has been very successfully used in many experiments covering a wide physics programme, for example the study of neutron-rich calcium nuclei in deep-inelastic reactions in inverse kinematics, the study of neutron-deficient nuclei around A~130 using fusion-evaporation reactions induced by radioactive beams, (d,p) reactions in inverse kinematics to study the evolution of single-particle states in the neutron-rich neon isotopes, and a successful test of the recoil-decay tagging method for the spectroscopy of heavy nuclei. The experience gained from these programmes both in physics and experimental techniques will be extremely useful for the coupling of AGATA to VAMOS. For the experimental programme at GANIL it is also mandatory to upgrade EXOGAM with digital electronics in order to allow for a smooth operation of the two systems.

Figure 3.4: Simulated RDDS spectra for the first excited states in 62Fe populated in the deep-inelastic reaction 238U + 64Ni at 6.5 A.MeV. Top: singles data (AGATA-1π in black and EXOGAM in red); Bottom: γγ coincidence spectrum gated on the 4+ state. The insets show the profile of the 2+ →0+ transition. Only gamma-rays emitted between 140° and 180° with respect to the direction of the reaction product have been taken into account.

Figure 3.4 shows a comparison of AGATA and EXOGAM employed for a Recoil-Distance Dopper-Shift measurement after a deep-inelastic reaction in inverse kinematics (238U+64Ni) which we have recently performed at GANIL in order to measure lifetimes in neutron-rich Fe isotopes. Due to a large gain in statistics, an improved background suppression and a better

energy resolution, AGATA will allow us to perform RDDS measurements of neutron-rich nuclei for the first time using γγ coincidences, thus avoiding ambiguities in the deduced lifetime due to side-feeding effects. Towards the end of the GANIL phase the array could be operating with the 1π configuration. Table 3.2 summarises the performance of the 1π array; this can be compared with Table 3.1. An immediate observation is that of the efficiency increase compared with the (Legnaro) Demonstrator, from 2.9% to 10.1% at 23.5 cm (an increase from 6.7% to 18.4% at 13.5cm). Even with the highest gamma-ray multiplicities the performance is excellent; this will be important for the studies of exotic shapes.

13.5 cm 23.5 cm Gamma-ray multiplicity 1 10 20 30 1 10 20 30 Efficiency (%) 18.4 14.4 12.9 11.7 10.1 8.7 7.9 7.3 Peak-to-Total 59.5 61.7 58.4 54.0 55.7 55.1 53.5 51.7 Recoil Velocity (v/c %) 0 5 10 50 0 5 10 50 Efficiency (%) 18.4 19.3 19.7 20.7 10.1 10.7 11.4 15.9 FWHM (keV) 2.5 2.6 3.0 10.1 2.5 2.5 2.7 6.7

Table 3.2 Performance of the 1π array at the two target-to-detector distances, 23.5 and 13.5 cm for 1 MeV gamma rays. The photopeak efficiencies and peak-to-total ratios are calculated for a multiplicities of 1, 10, 20 and 30. The photopeak efficiencies and resolutions (FWHM, keV) are calculated for recoil velocities (v/c) of 0, 5, 10, and 50%. 3.3 AGATA at GSI In the third science campaign of AGATA, the spectrometer will be installed at the GSI facility in Germany. In this campaign the science will be focussed on the unique very high-energy secondary beams from the UNILAC/SIS accelerator complex. At GSI the secondary beams of radioactive nuclei are produced by fragmentation of a range of stable primary beams and/or fission of a 238U beam on a 9Be or 208Pb target placed at the entrance of the fragment recoil separator (FRS). By 2012 the intensity upgrade required for the future FAIR facility will lead to a beam-intensity increase of a factor 102 to 103. Indeed, the operation of AGATA at GSI during this period will be part of the PreSpec project, the pre-cursor of the HISPEC (High-resolution In-Flight SPECtroscopy) project, which is part of the NuSTAR (Nuclear Structure, Astrophysics and Reactions) collaboration in FAIR. At GSI, the secondary beams are transported to the focal plane of the FRS where gamma-ray spectroscopy is performed using techniques such as relativistic Coulomb excitation and secondary fragmentation or few-nucleon removal reactions. The secondary beams are tracked through the FRS, and following reaction on a secondary target at the focal plane, are identified in terms of A and Z. This identification is performed using a calorimeter which on the timescale of this project will be LYCCA (Lund-York-Cologne CAlorimeter), which is presently under development for FAIR. The science campaign will be based on experience gained from experiments using the RISING gamma-spectrometer, consisting of 15 Cluster germanium detectors. A comparison between AGATA and the Cluster detectors that have been used in RISING is shown in Figure

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Figure 3.5: Comparison of experimental data (top left) and a simulation (lower left) for a relativistic Coulomb excitation experiment on 54Cr obtained with RISING with simulations for two AGATA configurations (5 modules top right and full array lower right).

3.5. The timescales of the GSI campaign are such that the 1π configuration of 45 detectors should be available. The calculations (Table 3.2) show that the photopeak efficiency of the 1π array is 20% for v/c = 0.5, with a resolution of 1%. This represents an increase of a factor of 12 in efficiency compared with RISING in singles and more than two orders of magnitude for coincidence spectroscopy. This will enable highly selective γ-γ-coincidences to be measured in fragmentation reactions, for the first time. The collaboration will investigate if the 15 RISING Cluster detectors should also be used for specific experiments. These could be located at backward angles to increase the efficiency, or mounted in a stand alone frame downstream of the target to efficiently detect decays from long-lived nuclear states (isomers) for specific experiments such as those aimed at the spectroscopy of heavy neutron-rich nuclei. As indicated in section 1.3 our physics programme at GSI is still in a planning stage, but the main emphasis will certainly lay on the evolution of shell structure very far from stability. Besides relativistic Coulomb excitation and few nucleon removal reactions we are planning to introduce the novel tool of inelastic proton scattering to populate excited states in nuclei furthest away from stability. Figure 3.5 shows the expected performance for two different AGATA (sub-)arrays for a relativistic Coulomb excitation experiment on 54Cr compared to a RISING experiment, which was performed a few years ago. Besides a gain in statistics the much improved energy resolution is the most remarkable feature, which will allow us to perform γγ coincidence measurements after reactions at relativistic energies for the first time. Moreover, the very visible one-neutron removal channel in the AGATA simulation shows the improvement in the sensitivity level.

4 Summary and request In this document we have laid out the current status and the future use of the first AGATA modules which have been developed within the R&D phase of the project and which are now (almost) ready for exploitation. We expect that results from a first successful test of the first full AGATA chain can be presented the CSTS meeting. After the commissioning and the first in-beam experiments achieving the final proof of gamma-ray tracking under real experimental conditions, the exploitation of the first AGATA modules should start in summer/fall 2009. While the AGATA Demonstrator is a powerful instrument in its own right it is also clear that only a swift increase in the number of available detectors will allow us to pursue our physics programme. As the construction of the complete AGATA array seemed a too ambitious goal at a time where major investment is needed for new large-scale facilities such as SPIRAL2 and FAIR, the collaboration has decided to plan the construction in several steps. In the years 2009-12 the construction of 1/3 of the full AGATA array is planned. The construction costs for this phase have been estimated to 12300 k€ (see also annex B of the new AGATA MoU, which is attached to this proposal). As for the Demonstrator the collaboration expects that the French institutes contribute ~20% of the total investment (2460 k€), which are to be shared between IN2P3, GANIL and Irfu. Since the parties to the new MoU will be DSM and IN2P3 a final decision of the sharing of the French contribution will have to be taken at that level. Here we indicate that the physicists from IN2P3 have agreed to request 50% of the expected French contribution. It seems unlikely that GANIL will be able to contribute at the 25% level as for the R&D phase during the construction of SPIRAL2. The SPhN physicists therefore believe that Irfu should contribute with 1/3 of the French contribution (820 k€) over four years (2009-12). The human resources needed in order to carry out the project are estimated for the next four years as

• 60 men-months for one engineer and one-to-two technicians at SEDI for building and maintaining the Ge detectors and the detector laboratory,

• 60 men-months at SIS for the construction and maintenance of the Detector Support System,

• 60 men-months of 3-4 physicists at SPhN to contribute to the technical developments (PSA etc.), the management of the project and to support the detector laboratory.

In order to preserve and foster our impact in the AGATA collaboration and to fully exploit the scientific potential of AGATA, we hope that the nuclear structure group will be strengthened in the near future by a qualified young scientist with interest and skills in the domain of gamma-ray spectroscopy.

Annexe A: List of Parties and Collaborating Institutions

Annexe A.1: List of Parties Univ. Sofia, Bulgaria; Bulgarian Academy of Sciences, Institute for Nuclear Research and Nuclear Energy, Bulgaria; Univ. Jyväskylä, Department of Physics, Accelerator Laboratory, Finland; Centre National de la Recherche Scientifique – Institut National de Physique Nucléaire et de Physique des Particules, France; Commissariat a l’Energie Atomique – Direction des Sciences de la Matière, France; Gesellschaft für Schwerionenforschung mbH, Germany; Istituto Nazionale de Fisica Nucleare, Italy; Polish Academy of Sciences – The Henryk Niewodniczanski Institute of Nuclear Physics, Poland; University of Warsaw, Poland; Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN/HH), Romania; Royal Institute of Technology, Stockholm, Sweden; Ankara University, Turkey; Science and Technology Facilities Council, UK; Each Party is representing their national institutions collaborating in the AGATA Project and takes the institutional responsibility for the Project with the exception of Bulgaria, France and Poland where each Party represents their own institutes or institutions.

Annexe A.2 List of Collaborating Institutions: Bulgaria: Univ. Sofia, INRNE Sofia Finland: Univ. Jyväskylä France: GANIL Caen, LPSC Grenoble, IPN Lyon, CSNSM Orsay, IPN Orsay, CEA/DSM/IRFU Saclay, IPHC Strasbourg

Germany: GSI Darmstadt, TU Darmstadt, Univ. zu Köln, TU München Italy: INFN Firenze, INFN Genova, INFN Legnaro, INFN Milano, INFN Napoli, INFN Padova, INFN Perugia (Camerino) Poland: IFJ PAN Krakow, University of Warsaw (HIL) Romania: IFIN/HH Bucharest Sweden: Chalmers Univ. of Technology Göteborg, Lund Univ., Royal Institute of Technology Stockholm, Uppsala Univ. Turkey: Univ. Ankara, Univ. Istanbul, Technical Univ. Istanbul UK: Univ. Brighton, STFC Daresbury Laboratory, Univ. Edinburgh, Univ. Liverpool, Univ. Manchester, Univ. Surrey, Univ. West of Scotland, Univ. York

Annexe B: AGATA Equipment, Capital Investment and Installation

Annexe B.1: AGATA Equipment and Capital Investment Each AGATA unit comprises a triple-cluster Ge detector with its associated electronics, data acquisition and storage system and related equipment. Specifications of all items will be produced by the AGATA management prior to production. All cost estimates are based on 2007 prices in Euro without tax. Definition of AGATA equipment: Germanium crystals: encapsulated, 36-fold segmented HPGe diode Triple-Cluster Cryostat (TCC): cryostat for three HPGe diodes incl. 111 preamplifiers Detector support system (DSS): high- and low-voltage supplies, auto-fill control system detector cabling, etc. Mechanics: mechanical support structure, individual frames etc. Digitiser module: stand-alone module for 36+1 high resolution Ge channels Pre-processing card: twin Carrier cards in ATCA standard with mezzanines Computer farm: PC farm and shared infrastructure General Trigger System (GTS): GTS cards Electronics infrastructure: ATCA crates etc. DAQ system: PC farm for DAQ including data storage Capital cost for the AGATA units: Item Cost/unit No Cost [k€] [k€] Ge crystals 160 3 480 Triple-Cluster Cryostat 80 1 80 Detector Support System 25 1 25 Digitiser modules 30 3 90 Pre-processing cards 30 3 90 General Trigger System 8 1 8 Computer farm 20 1 20 Cost per AGATA unit 793 Cost for 15 new AGATA units 11895 Capital costs for common items Item Cost [k€] Mechanics 150 Electronics infrastructure 150 DAQ system 100 Cost for common items 400 Total capital costs for 15 AGATA units 12295

Annexe B.2 Sharing of Capital investment and Human resources The Parties and/or Collaborating Institutions as appropriate are planning to make bids to contribute with the capital given in table B.2.1 for 15 new AGATA units and common items as given in annexe B.1. In-kind contributions will be made, whenever possible, allowing to make best use of the expertise and experience acquired during the R&D phase.

The participating collaborating institutions are planning to make human resources (physicists, engineers and technicians) as given in table B.2.1 available to the AGATA project (personnel in person-months during the period for construction, installation and commissioning of the 20 unit AGATA system).

Table B.2.1 Capital investment and human resources for construction, installation and commissioning of 15 new AGATA units, and planned sharing between the participating collaborating institutions of each country.

Country Planned capital investment in k€

Planned personnel in person months

Bulgaria 25 50 Finland 25 50 France 2460 450 Germany 2460 400 Italy 2460 500 Poland 25 50 Romania 180 50 Sweden 1640 200 Turkey 820 70 UK* 2460 550 Total 12555 2400

* In July 2008 the UK approved a first capital investment of 893 k€ and a Personnel investment of 470 person months. Capital investment and human resource commitments for prototyping and 5 AGATA units have been recorded since the start of the project. The information is reproduced in table B.2.2.

Table B.2.2 Capital investment and human resources committed for the AGATA R&D phase and the 5 unit AGATA system. The capital investment beyond 2007 is estimated.

Country Funds committed in k€

(2003-2008)

Personnel in person months (2003 - 2007)

Bulgaria 0 45 Finland 2 8 France 1400 1145 Germany 1228 336 Italy 1400 737 Poland 0 60 Romania 57 40 Sweden 850 175 Turkey 800 70 UK 950 455 Total 6687 3031

The Hosts will incur costs directly related to the installation and operation of the AGATA system. Estimates of these costs and the required human resources are given in table B.2.3. Table B.2.3 Capital investment without general infrastructure costs and human resources planned to be provided by the Hosts for the installation, commissioning and operation of AGATA assuming an 18 months operation period at each site.

Country Host Planned capital investment

[k€]

Personnel in person months

Italy LNL 230 150 France GANIL 190 101 Germany GSI 200 171

The total capital investment needed for the construction, installation and commissioning of the 20 unit AGATA system is summarised in table B.2.4. Table B.2.4 Summary table of the capital investment for the 20 unit AGATA system and the planned sharing between the participating collaborating institutions of each country, which comprises the planned investment for 15 new AGATA units, the funds committed until 2008 for the R&D phase, prototyping and 5 units, and the planned capital investment by the Hosts.

Country Planned capital investment

Funds committed (until 2008)

Planned capital investment by

the Hosts

Total capital investment

[k€] [k€] [k€] [k€] Bulgaria 25 0 0 25 Finland 25 2 0 27 France 2,460 1,400 190 4,050 Germany 2,460 1,228 200 3,888 Italy 2,460 1,400 230 4,090 Poland 25 0 0 25 Romania 180 57 0 237 Sweden 1,640 850 0 2,490 Turkey 820 800 0 1,620 UK* 2,460 950 0 3,410 Total 12,555 6,687 620 19,862

* In July 2008 the UK approved a first capital investment of 893 k€.

Annexe B.3: Construction schedule and Milestones Provisional planning and milestones for the construction of a 20 unit AGATA system in 4 years. The final planning will depend on the detailed funding profile and the delivery schedule of the Ge detectors which is to be negotiated with the manufacturer. Month Item 01 Start ordering of new AGATA Ge detectors and cryostats 07 Start production of new AGATA front-end electronics 12 AGATA system with 5 Triple-Cluster detectors completed 13 Begin delivery of AGATA Ge detectors and cryostats (at least 3 crystals every 2 months) 16 Begin integration of AGATA triple-cluster detectors (at least 1 cluster every 2 months) 30 Start upgrading AGATA DAQ system for 20 Triple-Cluster detectors 42 End delivery of new AGATA Ge detectors and cryostats 47 Integration of AGATA triple-cluster detectors completed 48 Installation of 20 unit AGATA system completed