RD1 Calorimeter Development for EIC: Progress report and funding request.

Oleg Tsai, UCLA (for EIC Calorimeter Consortium)

1’st part of the talk. 2’nd part will be given by C. Woody

EIC Generic R&D Advisory Committee Meeting, BNL Dec. 13 2012

• Progress Report. Part 1 – answering some questions raised during last meeting: “ There were concerns about proposal completeness, and the elucidation of calorimeter requirements

was lacking, specifically resolution, uniformity, calibration, rate capability, mechanical tolerances and radiation requirements. The Committee would like to understand transverse uniformity and spatial resolution of the test devices; it was not clear whether the in-beam measurements had been made with adequately fine determination of the position of the incoming particle and whether e.g. variation of the total energy response with incident particle transverse position could be determined.”  

For the first part, the Committee recommends the proposers return with a more developed request and that partial support be provided for a staff member to prepare this.” <- Specific to RD1

“Detector proponents need to note the radiation dose their proposed technology can withstand and discuss where further knowledge is needed. As a first step an analysis of the dose due to collision products alone is needed, not just as input to studies of overall dose but also to see if any technologies must be a priori ruled out.” <- General to all RD

We tried to addressed committee’s questions in details in the submitted proposal with the best knowledge we have now..

• General considerations: radiation hardness and neutron fluxes in the detector.

Preliminary estimations for rad. doses were made using same approach used for SSC and LHC detectors (scaling).

• [1] Groom, D. E. et al., Nucl. Instr. and Meth. A279, 1• [2] Stevenson, G. R., “New Dose Calculations for LHC Detectors”, Proc. ECFA

Large Hadron Collider Workshop, Aachen, Oct. 1990, CERN 90-10, ECFA 90-133, vol. II, p.566

Contacted an expert Y. Fisyak (BNL) who helped us to scale his STAR (RHIC) estimates for neutron fluences to EIC.

• Findings: a) Detailed descriptions of: detector, IP region, machine elements and

details of experimental hole and utilities will be required to get reliable numbers + measurements of thermal neutron rates at STAR IP region to normalize MC++ more detailed description will be required to find out detector performance in this environment.

b)Preliminary dose estimates and neutron fluxes for EIC seems to be comfortably low (any reasonable technology can be used).

Let’s look a bit more closer… “With such an approach, a crude estimate of the neutron flux for top

energy ep collisions with an integrated luminosity of 1041 cm-2 is ~1010 cm-2 at R= 7.5 cm at mid rapidity and at R=30 cm @ Z=8 m (forward rapidity up to ~5 for outgoing protons).”

How should we look at this numbers? Can we reject some technologies a priory? And can we tell how detector perform in this

environment?

We are proposing to use SiPM for compact readout R&Din year 2 of R&D program.

Half Full

The estimated level of neutron flux does not pose a challenge for EIC calorimeters readouts based on new version of HPK SiPMs.Necessary, but may be not sufficient…

Recent CMS R&D (CALOR 2012, J.Anderson (FNAL))

JLab, Hall D Barrel Calorimeter,arXive:1207.3743v2, C.Zorn et.al.

50 um cells

Half EmptyTexas Tower effect, 25 years later.To translate neutron flux numbers in detector performance requires quite a detailed description, which was not obvious for a while.

Another recent example:PANDA changed readout design they had in TDR after this CMS findings, despite extensive R&D when APDs were irradiated with protons, photons, neutrons.

D.A.Petyt, CALOR2012“Mitigation of anamaloussignals in the CMS ECAL.”

How all this related to ScFi calorimeters?

“Slow “ light collection from PWO required “by design” to reject second class of events.Would it be W/ScFi /APD design, second class of background event probably is impossible to reject.

“Early spikes” (t<0) are produced with the pp collision products.Some fraction are “non-isolated” causing the Swiss-cross cut to fail.“Late spikes” (t>0), chiefly produced by neutrons, are more likely tobe isolated.

D.A. Petyt, CALOR2012

• So, is this glass half empty or is it half full? Well…a)We probably can be cautiously optimistic with low level of

radiation doses and neutron fluxes in EIC detector (preliminary estimates).

b)We will not know these numbers well, until we have very detailed MC (details of IP, detector etc.). (Flanges in the beam pipe, DX, ZDC (for STAR, as an example)) + controlled measurements.

c) How (b) will translate in detector performance even more complicated, because that may require details at level of a thickness of a ~100 um protective epoxy layer at sensors.

On the positive side: CMS is able to reproduce almost all effects now in their MC (hunt for last hydrogen atom was successful).

• What would be the right direction for R&D for compact readout of EIC calorimeters (sensors) without guidance from (b) and (c) for a while (being realistic)?

XIV International Conference on Calorimetry in High Energy Physics (CALOR 2010), Piece of wisdom (IMHO)

R. Wigmans “Hadron Calorimetry – what have we learned since CALOR1?”

4.1. Avoid repeating mistakes from the past Since progress in the field of hadron calorimetry depends entirely on experimental trial-and-error exercises, it is very important that people or groups engaged in this effort are aware of the history, if only to avoid repeating mistakes from the past. Unfortunately, this is not always the case, as I will illustrate with two well documented examples.

One should avoid placing readout elements that may produce HUGE signals for one particular type of shower particle in the path of a developing shower. This may lead to a phenomenon that has become known as the “Texas Tower effect” , first observed in the forward calorimeter of the CDF experiment [21, 22, 23]. In this device, recoil protons from elastic neutron scattering deposited up to 1 MeV in an active (gas) layer, which because of the very small sampling fraction ( 10−5) appeared as an energy deposit of 100 GeV in a single calorimeter cell. Such “hot spots” were recently also observed in the ECAL of the CMS experiment. The culprits are in that case densely ionizing particles from a nuclear reaction, such as depicted in Figure 5. Such nuclear fragments have dE/dx values that are typically 100-1000 times larger than for a mip. When traversing the

APD which detects the scintillation light from the PbWO4 crystals constituting the ECAL, such (MeV type) particles may generate signals that are 100 000 times larger that that from a scintillation photon, and thus fake energy deposits of tens of GeV.

We don’t want to see “Texas Tower effect” at EIC, this is one of the reasons to go with MPPCs for proposed R&D for compact readout of sampling calorimeters for EIC. (MPPC considered to be neutron insensitive).

This will pose difficulties at short term (next year) but seen at present as a preferable direction for future developments.

The radiation doses in calorimeters of central detector are very low (few kRad, ScFi calorimeters were proposed for 6 MRad environment), practically any reasonable technology can be used (however, the topic of radiation damages is very complex and in future we are planning to come back to this question again).

• Questions specific to RD1“Proof of principle” – resolution close to MC predictions once impact area was kept wide (All possible instrumental effectsof W/ScFi compound in this case automatically included).

Complications related to pixilation (light collection efficiency and light collection uniformity) was set aside at first year R&D because these are not completely trivial questions. “One step at a time” – approach.

“Global”Instrumental Effects. MC for W/ScFi type. Common for any type of EIC calorimeters.

At low energy region it is very hard to separate them (except of photostatistics) , at high energy they becomes dominant factors, easy to see.

A)Uniformityof LightCllection

B)Efficiencyof LightCllection.

Things we rightfully decided not to worry about last year.

WLS Plates Short Light Guide

The second important measurement during first year of R&D was absolute light yield,which was found to be 2000 pe/GeV (with, probably, 100% efficiency of light collection).

First attempts during Summer 2012 with summer students at UCLA ( and at BNL)didn’t bring an adequate solution for compact scheme of light collection yet.Efficiency is low ~10%, uniformity is 6% (rms).

Both RD1 and BNL groups come to the same conclusion, WLS plates will not workfor geometry we wanted to test in 2013.

About half of the scintillation light willnot be absorbed in WLS plate.This is the reason for hot spots under theSensors.

The uniformity of the light collection is sensitive to the angular distribution of lightintensity of the light source whichwas used in our setup.

For (A) type we got 6% rmsFor (B) type we got 3% rmsHint for future optimizations.

Another summer student attempted to reproduceExperimental results with MC, didn’t work.

• Light collection efficiency. Goal is to reach at least 500 pe/GeV in next year.

• Driven by energy resolution ~10%/sqrt(E) (to understand technology limitations, first iteration of reference detector, Elke’s talk)

• DVCS low energy cutoff at 1 GeV (Elke’s talk)• Year 2 of R&D, complications with pixilation. Cluster 3x3, tower

size about 1 Rm. Gives about 25 MeV in side towers- 12 p.e. for projective geometry, may be OK.

• For non-projective geometry for central barrel this number may be marginal (in this case we’ll be dealing with 3D shower profiles), need to run stand alone MC.

• The cluster algorithms and noise level has to be included in next round of stand alone MC to continue investigation of instrumental effects for sampling calorimeters of EIC, in particular, to set requirements for light yield (request to support post-doc).

• Plan for R&D. Without clever solution for compact readout so far, we want to be conservative:

a) Use multi-clad fibers (better trapping efficiency, 50% more compare to single clad, that will improve overall efficiency; wider angular distribution should help with uniformity, if hint from summer studies is correct).

b) Use MPPC, PDE is better compare to SENSL SiPM (about factor of two)

c) Re-arrange fibers within a single tower same way it is done for super-module in year 1, may improve both efficiency and uniformity, or may not.

d) The most obvious solution as to increase the size of the sensors dose not seen as a right way to proceed at this time (this is our last reserve).

e) Another reserve is to boost sampling fraction.

Conceptual design for optical, mechanical, electrical and monitoring integration for the W/ScFi calorimeter.New group from IUCF joined calorimeter group.

∑ amplifier for four SiPMs and Thermo-compensated bias for SiPMs.Bridged to existing DAQ (ADC) for the test run.

BNL and IUCF will work on FEE design for the test Run at SLAC in parallelwith the work already in progress forsPHENIX.

IUCF, feasibility check

Summary:

Division of responsibilities:RD1 - will construct barrel prototype, 3x5 matrixBNL/IUCF- front end electronics for test runAll – help with “global” simulationsAll – test beam

Budget Request.

Status of R&D on W-SciFi Calorimeters for EIC at BNL

E.Kistenev, E.Mannel, S.Stoll, A.Sukhanov, C.Woody

PHENIX Group

Physics DepartmentBrookhaven National Lab

EIC Detector R&D Committee Meeting

December 13, 2012

C.Woody, EIC Detector R&D Committee, 12/13/12 23

Relationship to the UCLA W-SciFi R&D Effort• The BNL PHENIX Group is currently pursuing an alternative

(although similar) approach to the UCLA design to build a tungsten-scintillating fiber electromagnetic calorimeter which could be used at EIC

• Uses common components with the UCLA design: Tungsten powder epoxy (although much less, since it also

uses tungsten metal absorber plates) Plastic scintillating fiber SiPM readout

• Common issues: Light yield and light collection from fibers Use of SiPMs (control of bias voltage & temperature

compensation) Readout

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Tungsten SciFi Epoxy Sandwich

Scintillating fibers~ 0.5 – 1.0 mm

Pure tungsten metal sheet (r ~ 19.3 g/cm3) Thickness ~ 0.5-1.0 mm

Tungsten powder epoxy (r ~ 10-11 g/cm3)

Uniform thickness, thin pure tungsten metal sheets with wedge shaped SciFi + tungsten powder epoxy layer in between

Can be made into large modules (> 1m)

C.Woody, EIC Detector R&D Committee, 12/13/12

10 cm

X0 = 5.3 mm RM = 15.4 mm

~ 18 X0

Fibers extended for light output measurements

C.Woody, EIC Detector R&D Committee, 12/13/12 25

Discoveries over the past 6 months

1. 1 mm tungsten plates undergo some deformation (spring-back) when bent into the accordion shape

2. The scintillating fiber/W-powder epoxy layer is rather weak and cannot hold the shape of the accordion when the W-plates are glued onto it

3. As a result of 1) & 2) and the type of glue used to join the plates and SciFi layer together, the sandwiches can easily come apart

4. The present idea is to use tapered tungsten plates (possibly two or three thin plates laminated together) with a uniform thickness SciFi layer (e.g., SciFi ribbons) in between

5. New types of glues are also being explored

C.Woody, EIC Detector R&D Committee, 12/13/12 26

New 3 Layer Sandwich Approach Single taper thickness plate in the center

Glue two uniform thickness plates top and

bottom

New adhesives tested show > 1400 PSI tensile strength

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Light Yield from Fibers Need sufficient light output from fibers to allow randomizing and collecting

the light onto a small readout device

C.Woody, EIC Detector R&D Committee, 12/13/12

~ 200 p.e./MeV of energy in scintilator(~ 100 p.e./MeV from UCLA beam test)

Need to reduce cladding light to flatten response

Ends blackened to reduce light near readout end

Light output depends on glue and fiber type

~ 2000-4000 x (Light Collection

Factor) p.e./GeV in calorimeter

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Light Collection and Randomization

C.Woody, EIC Detector R&D Committee, 12/13/12

fibers

SiPM lucite• 21x21x19 mm lucite block• Wrapped on 5 sides with white teflon• SiPM centered on one 21x19 mm face• No couplant between SiPM and block• White paint on surface between fibers

Black surface SiPMSpectralon cavity

fibers

• 21x21x10 mm Spectralon cavity• SiPM 6 mm above base• Black surface between fibers

Testing light mixer configurations with single SiPM

100% = 1.9% absolute efficiency

100% = 3.7% absolute efficiency

Trade off between uniformity and efficiencyArea match of a 2x2 cm tower with a single 3x3 mm SiPM = 2.1 %

Will test with multiple SiPMs

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Readout Devices

C.Woody, EIC Detector R&D Committee, 12/13/12

• Currently investigating SiPMs from a number of different manufacturers• Hamamatsu (3x3 mm2)• SensL( 6x6 mm2)• AdvanSiD (formerly FBK)• RMD (5x5 mm2)• Zecoteck• Excelitas

HamamatsuS10362-33-25C

3x3 mm2 14.4K 25 mm pixels

Gain ~ 2 x 105

PDE ~ 25% @ 440 nm

Areas for improvement:• Larger dynamic range, better linearity• Higher PDE• Faster recovery

New Hamamatsu 15 mm pixel device being developed for CMS (new technology)

MPPC-154489 15 mm pixels/mm2

Gain ~ 2 x 105

PDE ~ 20% @ 515nmtR ~ 11 ns

Currently only available in 1x1 mm2

Expect to have first 3x3 mm2 early next year

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Readout Electronics

C.Woody, EIC Detector R&D Committee, 12/13/12

• New SiPM readout system being developed for sPHENIX• Preamp (voltage amplifier)• Temperature sensor (thermistor) for each SiPM• Feedback to bias voltage for temperature stabilization and control• Also developing 12 bit ADC

Preamp circuit

Block diagram of control circuit

Prototype readout board

12 bit

Output response (input = LED)Blue = SiPMRed = Preamp output

Need to develop new system for multiple SiPMs

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R&D Goals for 2013• Decide on absorber plate fabrication process and produce plates

• Complete tests on adhesives for bonding plates together and fibers to plates

• Continue measurements to optimize light output and uniformity from fibers embedded in glue and from light collector. Start looking at multiple SiPM readout.

• Design new readout electronics for multiple SiPMs (no changes to preamp, only passive summation of SiPM signals and changes to temperature monitoring and bias control).

• Build small (~ 5x5 tower) prototype detector (or possibly more than one with different sampling fractions)

• Test prototype detector(s) in a test beam in the second half of 2013

C.Woody, EIC Detector R&D Committee, 12/13/12

Backup Slides

Work in progress…

Dimensions 20.5 mm x 20.5 mm x tbd mmSiPM 4x Hamamatsu S10931-025POutput connector MMCXOutput characteristics AC coupled, 50 Ω, to drive 50 Ω load, negative

polarity for ease of interface to standard ADC modules

Amplifier risetime <5 nsFull scale range >15000 pixels fired in one pulseBias voltage trim range +/- 10 VBias voltage trim adjustability each SiPM independently, resolution <20 mVBias voltage stability <10 mV (at constant temperature)Gain stabilization Temperature compensated bias voltageBias voltage temperature coefficient Fixed by design, not adjustablePower input +3.0 V, −2.0 V, −90 VPower dissipation (amplifier) 40 mWPower dissipation (bias regulator) 40 mWControls interface 1-wire bus protocolPower/controls connector 5 pins microminiature wire connector, e.g.

Samtec T1M-05…

Table of key requirements and potential specifications