25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 11/30/30
R&D for the next generationR&D for the next generationof gaseous photon detectors of gaseous photon detectors
for Imaging Cherenkov Countersfor Imaging Cherenkov Counters
TodayToday’’s generation of gaseous PD, s generation of gaseous PD, their limitations their limitations and the way outand the way out
The R&D lab studiesThe R&D lab studies
Our plans for futureOur plans for future
Jarda Polak(INFN Trieste and TUL Liberec)
TodayToday’’s generation of gaseous PD, s generation of gaseous PD, their limitations their limitations and the way outand the way out
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 22/30/30
Photon Detectors used for Photon Detectors used for RICHsRICHsbelong to three categories:belong to three categories:
Vacuum based Vacuum based PDsPDsPMTSPMTS ((SELEXSELEX, , HERMESHERMES, , BaBarBaBar))MAPMTsMAPMTs ((HERAHERA--BB, , COMPASSCOMPASS))Flat panelsFlat panels ((various test beams, proposed for CBMvarious test beams, proposed for CBM))HybrideHybride PMTsPMTs ((LHCbLHCb))MCPMCP--PMT (PMT (all the studies for the high time resolution applicationsall the studies for the high time resolution applications))
Gaseous Gaseous PDsPDsOrganic vapours: TMAE and TEA (Organic vapours: TMAE and TEA (DELPHIDELPHI, , OMEGAOMEGA, , SLD CRIDSLD CRID, , CLEO IIICLEO III))Solid Solid photocathodesphotocathodes: : CsICsI ((HADESHADES, , COMPASSCOMPASS, , ALICEALICE, , JLABJLAB--HALL A, HALL A, PHENIXPHENIX))
Si Si PDsPDsSilicon Silicon PMsPMs ((first tests only recentlyfirst tests only recently))
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 33/30/30
photoconvertingphotoconverting vapours are no longer in use, a part CLEO IIIvapours are no longer in use, a part CLEO III(rates ! time resolution !)(rates ! time resolution !)
the present is represented by MWPC (open geometry!) with the present is represented by MWPC (open geometry!) with CsICsIthe first prove (in experiments !) that coupling solid photocathodes and gaseous detectors worksSevere recovery time (~ 1 d) after detector trips ion feedback Moderate gain: effective gain ~ 104 CsI ionAging bombardment (see below)
The way to the future: The way to the future: ion blocking geometriesion blocking geometriesGEM/THGEM allow for multistage detectors
With THGEMs: High overall gain ↔ pe det. efficiency!Good ion blocking (up to IFB at a few % level)MHSP: IFB at 10-4 level
opening the way to:Gaseous detectors with solid photocathodes for visible light
First step in this direction: PHENIX HBD
PASTPAST
PRESENT
PRESENT
FUTURE
FUTURE
Large sensitive areas Large sensitive areas --> gaseous PD> gaseous PD(the only cost affordable solution)(the only cost affordable solution)
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 44/30/30
MWPCs with CsI photocathodes in COMPASS:beam off: stable operation up to > 2300 Vbeam on: stable operation only up to ~2000 V(in spill ph. flux: 0 - 50 kHz/cm2 , mip flux: ~1 kHz/cm2)
Whenever a severe discharge happens, recovery takes ~1 day.Similar behavior reported from JLAB Hall-A
1) Moderate gain
Limitations of recent generation Limitations of recent generation -- MWPCMWPC
Source of the problem: ion bombardment of photo-converting layer
this limits the time
this limits the time
The MWPCThe MWPC
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 55/30/30
0 1 2 3 4 5 6 7 8 9 100
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
measurementlognormal fitcomparison to previous method
accumulated charge [mC/cm2] within pos 1
decr
ease
in p
hoto
-cur
rent
[%]
f_p1_nr2 x( ) F x 0.856, 1.695,( ):= chi2 fi0 fi1,( ) 0.404=
Q.E. degradation vs charge
H. Hoedlmoser et al., NIM A 574 (2007)28; H. Hoedlmoser, CERNH. Hoedlmoser et al., NIM A 574 (2007)28; H. Hoedlmoser, CERN--THESISTHESIS--20062006--004004
2) Ageing - first observed at COMPASS- detailed study by Alice team
10 10 µµmm
normalnormal ““white stripwhite strip””CsI surface at microscope (x 1000)
due to ion bombardment - ageing at few mC/cm2
this limits the rate
this limits the rate
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 66/30/30
GAS ELECTRON MULTIPLIER (GEM)GAS ELECTRON MULTIPLIER (GEM)Thin metalThin metal--coated polymer foils coated polymer foils 70 70 µµm holes at 140 m holes at 140 µµm pitchm pitch
F. Sauli, NIM A386(1997)531
Manufactured by standard PCB techniques of precise drilling and Cu etching.
ECONOMIC & ROBUSTECONOMIC & ROBUST
There is need of new technologyThere is need of new technology
Possible solution – closed geometriesto overcome recent limits – fight ion bombardment and photon feedback
GEMsGEMs and and THGEMsTHGEMs
1mm
Chechik et al. NIM A535 (2004) 303C. Shalem et al. NIM A558 (2006) 475
& NIM A558 (2006) 468
GEMGEM’’ss principleprinciple
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 77/30/30
Examples of ion blocking schemes from literature- Similar schemes can be adopted with THGEM
multiGEMmultiGEM with with Reflective photocathodeReflective photocathode
Electron’s path Ion’s back-flow
ElectronsElectrons
IonsIons
60 %
40 %
MultiGEMMultiGEM’’ss::ion blocking + high GAINion blocking + high GAIN
Simulation of avalancheSimulation of avalanche
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 88/30/30
h3Entries 44448Mean 0.9679
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
200
400
600
800
1000h3
Entries 44448Mean 0.9679
Polya 0
h5Entries 44448Mean 1.006
100
200
300
400
500
600
700
800h5
Entries 44448Mean 1.006
Polya 0.8
3.5 4 4.5 5 0 0.5 1 1.5 2 2.50
100
200
300
400
500
600
h7Entries 44448Mean 0.9993
3.5 4 4.5 5
h7Entries 44448Mean 0.9993
0 0.5 1 1.5 2 2.50
200
400
600
800
1000
1200
Polya 5
h9Entries 44448Mean 0.9992
h9Entries 44448Mean 0.9992
500
1000
1500
2000
2500
Polya 30
Signal amplitude follows Signal amplitude follows PolyaPolya distribution:distribution:
Threshold always critical !Threshold always critical ! With good electronics:With good electronics:Limited Limited pepe detection efficiency,detection efficiency, threshold no longer criticalthreshold no longer critical
good good pepe detection efficiencydetection efficiencyperformance instabilitiesperformance instabilities stable behaviourstable behaviour
Gain Gain ≈≈ 101066Gain Gain ≈≈ 101044
thresholdthreshold thresholdthreshold
The relevance of high GAINThe relevance of high GAIN
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 99/30/30
Why do we try with Why do we try with THGEMsTHGEMsand reflective photocathode?and reflective photocathode?
No need of high space resolution ( > 1 mm)Large area coverage (5.5 m2 for COMPASS RICH)
- industrial production- stiffness- robust against discharge damages
For reflective photocathodes,-no need to keep the window at a fixed potential (2nm Cr -20%)-possibility of windowless geometry-higher effective QE (larger pe extraction probability)
small photoconversion dead zones (<20%; GEM ~ 40%)Large gain
goal: SINGLE PHOTON detectiongoal: SINGLE PHOTON detection
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 1010/30/30
EXAMPLES OF THGEMSEXAMPLES OF THGEMS
R3
P1
W2
P1:D=0.8 mmPitch=2 mmRim=0.04 mmThick=1mm
R3:D=0.2 mmPitch=0.5 mmRim=0.01 mmThick=0.2mm
W2:D=0.3 mmPitch=0.7 mmRim=0.1 mmThick=0.4mm
A MULTIPARAMETER SPACE TO EXPLORE !A MULTIPARAMETER SPACE TO EXPLORE !4 geometrical parameters4 geometrical parameters: : diameter pitch rim thicknessdiameter pitch rim thickness+ + materialmaterial + + production procedureproduction procedure
24 different
24 different THGEMs
THGEMs characterized so far
characterized so far
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 1111/30/30
THGEM multipliersTHGEM multipliersManufactured by standard PCB techniques of precise drilling (different materials) and Cu etching.
0.1mm RIM: prevents discharges high gains!
1mm
101055 gain in single-THGEM ELTOS S.p.A. (Arezzo, Tuscany)http://www.eltos.it/en/main/en-main.htm
Small diameter holes high rotation speed of the driller. Multi-spindle machines at
ELTOS reach 180000 turns/min hole diam. down to 150 µm.
Nominal drilling tolerance: +- 10 µm
POSALUX ULTRASPEED 6000LZ6-spindle-roboter
= GEM like structure with expanded dimensions
Example of production..Example of production..Example of THGEMExample of THGEM
We are testing samples made at:We are testing samples made at:Weizmann Institute (Israel)Weizmann Institute (Israel)CERN (CERN (RuiRui de Oliveira)de Oliveira)EltosEltos S.p.AS.p.A. (Italy). (Italy)
cross section of one hole
Cu layer
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 1212/30/30
small prototypes small prototypes –– activeactivesurface (30 x 30) mmsurface (30 x 30) mm22
1 THGEM layer for this activity1 THGEM layer for this activity
ANODEV0
V1
V2
V3
THGEMtoptop
ThGEM
55Fe source
Configuration inside the chamber
Used Gas: Ar/CO2 70/30 %
THGEM
Test chamber
To detect ionizing particle :V3< V2< V1<V0
CHARACTERIZATION CHARACTERIZATION
Edrift
Einduction
CATHODE
∆V bottombottom
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 1313/30/30
LAB STUDIES AT CERN AND TRIESTELAB STUDIES AT CERN AND TRIESTE
so far using Cu Xso far using Cu X--ray ray spectra are collectedspectra are collectedcurrents are measured at HVcurrents are measured at HV
homemade instruments (~200 €)with ~1 pA resolution data collection via pictures and image recognition
0 200 400 600 800 1000 1200
0
20
40
60
80
100
120Data: A7WOR063_BModel: Gauss Chi^2/DoF = 8.71997R^2 = 0.98288 y0 0 ±0xc1 358.38194 ±1.127w1 59.83813 ±2.33596A1 1173.67306 ±38.88758xc2 490.61839 ±0.18222w2 67.19041 ±0.38037A2 8612.61426 ±41.12351
Cou
nts
ADC channels
Energy Spectrum
CMOS Operational Amplifier: AD 8607
10 MΩ feedback resistor: VISHAY CNS020(+- 0.02%, +- 10 ppm/ºC)
1 nF to 100 nFfeedback capacitor
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 1414/30/30
What we have learned so farWhat we have learned so far1)1) Gain stability vs. RIM Gain stability vs. RIM
RIM: 0.1 mm
RIM: 0
RIM: 0.1mmLong time GAIN variation
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 1515/30/30
1)1) Gain stability vs. RIM Gain stability vs. RIM
RIM: 0.1 mm
RIM: 0
Long time GAIN variation
Short time GAIN variation – irradiation at HV switch ON (after ~1 day with NO voltage)
RIM: 0RIM: 0.1 mm
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 1616/30/30
1)1) Gain stability vs. RIM Gain stability vs. RIM
RIM: 0RIM: 0.1 mm
RIM: 0.1 mm
RIM: 0
Long time GAIN variation
Short time GAIN variation – irradiation after ~10 hour at nominal voltage without irradiation
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 1717/30/30
1)1) Gain stability vs. RIM Gain stability vs. RIM
RIM: 0.1 mm
RIM: 0
Long time GAIN variation
Short time GAIN variation
RIM: 0RIM: 0.1 mm
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 1818/30/30Silvia DALLA TORRESilvia DALLA TORRECOMPASS COLLABORATION MEETING, CERN, 22COMPASS COLLABORATION MEETING, CERN, 22--23/5/200823/5/2008
…… also also GEMGEM’’ss are not so stable are not so stable ……
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 1919/30/30
2) 2) Larger Larger RIMsRIMs allow higher gains allow higher gains ……
1.3 1.4 1.5 1.6 1.7 1.8100
1000
Gai
n
Delta V (KV)
THGEM electro-chem. polished without rim THGEM without rim THGEM with rim=0.1mm THGEM made of kapton THGEM with different geometry
PARAMETERS:• Diameter = 0.3 mm• Pitch= 0.7 mm• Thickness = 0.4 mm• Rim = variable• Gas: Ar/CO2 – 70/30
RIM: 0
RIM: 0.01 mm
RIM: 0.1 mm
GA
IN
∆V [ kV ]Large RIM <Large RIM <--> large GAIN and instabilities
> large GAIN and instabilities
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 2020/30/30
2)2) but but increasing THICKNESS increasing THICKNESS does it toodoes it too
1.3 1.4 1.5 1.6 1.7 1.8100
1000
Gai
n
Delta V (KV)
THGEM electro-chem. polished without rim THGEM without rim THGEM with rim=0.1mm THGEM made of kapton THGEM with different geometry
PARAMETERS:• Diameter = 0.3 mm• Pitch= 0.6 mm• Thickness = 0.6 mm• Rim = 0 mm• Gas: Ar/CO2 – 70/30
PARAMETERS:• Diameter = 0.3 mm• Pitch= 0.7 mm• Thickness = 0.4 mm• Rim = variable• Gas: Ar/CO2 – 70/30
GA
IN
∆V [ kV ]
““ThickerThicker”” THGEMS looks promising
THGEMS looks promising
RIM: 0
RIM: 0.01 mm
RIM: 0.1 mm
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 2121/30/30
3)3) Are THGEM devices for Are THGEM devices for HIGH RATESHIGH RATES ??
0 20 40 60 80 100 120-200
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Cu
rren
t (p
A)
Rate (KHz)
RECALL:RECALL:120 kHz/ mm120 kHz/ mm22, 300 e, 300 e-- single photoelectron rates of single photoelectron rates of ~35 MHz/ mm~35 MHz/ mm22
120 kHz / mm120 kHz / mm22
0 20 40 60 80 100 120
2000
2500
3000
3500
4000E
induction=3.5 KV/cm, E
drift=1.5 KV/cm
Gai
nRate (KHz)
Delta V=1.725 KV Delta V=1.775 KV Linear fit of Delta V=1.725 KV data Linear fit of Delta V=1.775 KV data
120 kHz / mm120 kHz / mm22
PARAMETERS:• Diameter = 0.3 mm• Pitch= 0.7 mm• Thickness = 0.4 mm• Rim = 0.1 mm• Gas: Ar/CO2 – 70/30
20%20%
PARAMETERS:• Diameter = 0.3 mm• Pitch= 0.7 mm• Thickness = 0.4 mm• Rim = 0 mm• Gas: Ar/CO2 – 70/30
Rate is not a limitation
Rate is not a limitation
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 2222/30/30
RIM: 0.01 mm
0 2
200
300
400
500
600
700
800
900
1000
1100
1200 THGEM: d=0.3 mm, p=0.7mm, rim=0mm, t=0.4mm; DeltaV=1.35 KV THGEM: d=0.3 mm, p=0.7mm, rim=0mm, t=0.4mm; treated electro-chem.; DeltaV=1.45 KV THGEM: d=0.3 mm, p=0.7mm, rim=0.1mm, t=0.4mm; DeltaV=1.775 KV
Edrift
(KV/cm)
Gai
n
2000
2500
3000
3500
4000
4500
5000
5500
6000
6500
Gain
DRIFT SCAN
RIM: 0
RIM: 0.01 mm
RIM: 0.1 mm
0 0.5 1. 1.5
PARAMETERS:• Diameter = 0.3 mm• Pitch= 0.7 mm• Thickness = 0.4 mm• Rim = variable• Gas: Ar/CO2 – 70/30
4)4) Tuning theTuning the fieldsfieldsfocusing electrons into the holesfocusing electrons into the holes
GA
IN
Edrift [ kV/cm]X-Ray Source: ~1 mm2, rate ~1.7KHz.
GA
IN
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 2323/30/30COMPASS COLLABORATION MEETING, CERN, 22COMPASS COLLABORATION MEETING, CERN, 22--23/5/200823/5/2008
EEinductioninduction changes thechanges thecharge shearing charge shearing between THGEM between THGEM bottom and anodebottom and anode
4)4) Tuning the Tuning the fieldsfieldsbottom/anode current sharingbottom/anode current sharing
∆V
ElectronsElectrons
IonsIons
60 %
40 %
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 2424/30/30
THGEM
protection box
CsICsI evaporation at CERNevaporation at CERN(A. Braem, C. David, M. van Stenis)(A. Braem, C. David, M. van Stenis)
Approaching our goalApproaching our goal-- detect UV photonsdetect UV photons……
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 2525/30/30
THE SMALL PROTOTYPE STRUCTURE THE SMALL PROTOTYPE STRUCTURE wireswires
11stst THGEM (THGEM (CsICsIhere,externalhere,externalface)face)
22ndnd THGEMTHGEM
collection anodecollection anode
apertures for gas apertures for gas circulationcirculation
readread--outout
Quartz radiator(truncated cone)
…… Cherenkov photonsCherenkov photons……
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 2626/30/30
TEST BEAM SETTEST BEAM SET--UPUPFOR SMALL FOR SMALL PROTOTYPESPROTOTYPES
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 2727/30/30
PerspectivesPerspectivesShort term plans:
- optimize the parameters of the THGEM with photoconverting CsIlayer to achieve maximum photoelectron collection efficiency
- optimize the parameters for the (double) THGEM to be used forthe amplification of the signal to provide large and stable gain
- produce a set 600 x 600 mm2 THGEMs and assemble them withstesalite spacer frames into first complete “full size” prototype chamber
Possible medium term project:- Upgrade of COMPASS RICH (~4m2) with the new photon detectorsin case the COMPASS Collaboration decides for it.
Longer term dream:- find a configuration to reduce the ion back-flow down to <10-5
and operate this large area detectors with visible photoconverter
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 2828/30/30
600 mm
600 mm
THGEMsStesalite frames
1500 mm
Al frame
Anode pads
There is hope to use these detectors for detection of visible photons
……wewe’’re building full size prototype re building full size prototype
= COMPASS RICH1 size= COMPASS RICH1 size
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 2929/30/30
ConclusionsConclusionsA third generation of gaseous Photon Detectors for RICHapplications, based on micropattern gas detectors, isexpected to overcome the performance limits of MWPC’scoupled with CsI photocathodes.THGEM seem to be very promising: they are stiff, robustand suitable for industrial production; they are expectedto provide high gain, small dead areas and very goodphotoelectron collection efficiencies.An effort to characterize these novel detectors has startedwith the aim to optimize geometrical parameters, productionprocedures and working conditions for large area coverage.A full size 600 x 600 mm2 prototype will be produced,assembled and tested in the incoming months.
25/07/2008 25/07/2008 -- SPIN 2008 PRAHA SPIN 2008 PRAHA 3030/30/30
Thanks to the help from many colleaguesThanks to the help from many colleagues……
M. Alexeeva, R. Birsab, F. Bradamantec, A. Bressanc, M. Chiossod,P. Cilibertic, G. Crocie, M. Colantonif, S. Dalla Torreb, S. Duarte Pintoe,O. Denisovf, V. Diazb, N. Dibiased, V. Duicc, A. Ferrerod, M. Fingerg,M. Finger Jrg, H. Fischerh,G. Giacominii,b, M. Giorgic, B. Gobbob,R. Hagemannh, F. H. Heinsiush, K. Königsmannh, D. Kramerj, S. Levoratoc,A. Maggioraf, A. Martinc, G. Menonb, A. Mutterh, F. Nerlingh, D. Panzieria,G. Pesaroc, J. Polakb,j, E. Roccod, L. Ropelewskie, P. Schiavonc, C. Schillh, M. S lunecka j , F . Sozz i c , L . Ste iger j ,M. Sulc j , S . Takekawac,F. Tessarottob, H. Wollnyh
a INFN, Sezione di Torino and University of East Piemonte, Alessandria, Italyb INFN, Sezione di Trieste, Trieste, Italyc INFN, Sezione di Trieste and University of Trieste, Trieste, Italyd INFN, Sezione di Torino and University of Torino, Torino, Italye CERN, European Organization for Nuclear Research, Geneva, Switzerlandf INFN, Sezione di Torino, Torino, Italyg Charles University, Prague, Czech Republic and JINR, Dubna, Russiah Universität Freiburg, Physikalisches Institut, Freiburg, Germanyi University of Bari, Bari, Italyj Technical University of Liberec, Liberec, Czech Republic
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