Study of GEM-like detectors with resistive electrodes for

RICH applications

A.G. Agocs1, A. Di Mauro2, A. Ben David3, B. Clark4, P. Martinengo2, E. Nappi2,5 ,

V. Peskov2,6, 1Eötvös University, Budapest, Hungary

2CERN, Switzerland3Tel Aviv University, Israel

4North Carolina State University, USA5Bari University

6 Ecole Superior des Mines, St Etienne, France

1

Recent results from RHIC as well as numerous theoretical predictions indicate that a very high

momentum particle identification (VHMPID) may be needed in the future ALICE experiments.

In connection to this the ALICE-HMPID collaboration is studying the possibility to make a new detector to identify charged particles with momentum p > 5÷10 GeV/c VHMPID (Very High Momentum Particle Identification Detector).

Several Cherenkov detector designs were preliminary considered and simulated by the ALICE VHMPID

collaboration : a threshold type as well as a RICH type

(see G. Volpe talk at this Conference).

2

One of the complication- there is a very limited space available for

VHMPID

So only compact and simple VHMPID designs can be

considered

3

Focusing setupThe focusing properties of a spherical mirror of radius R = 240 cm, are exploited. The photons emitted in the radiator are focused in a plane that is located at R/2 from the mirror center, where the photon detector is placed.

(from G. Volpe talk at this Conference). 4

One of the promising photodetector element in this RICH design could be GEM-like

detectors combined with CsI photocathodes

Advantages :

● They are compact● Can operate at higher gains and in badly quenched gases including inflammable gases● Can be used in the same gas as a radiator● Have high QE● Have potential for higher special resolution

5

For the last several years we were focused on developing

more robust GEM-like detectors for RICH application

6

First attempt-”Optimized”/Thick GEM

Further development of this detector was performed by Breskin group- see R. Chechik presentation

7

Photo of one of the “optimized” or “thick GEM” developed by us earlier

L. Periale et al., NIM A478,2002,377 J. Ostling et al., IEEE Nucl. Sci 50,2003,809

TGEM is manufactured by standard PCB techniques of preciseprecise drilling drilling in G-10 (+ other materials) and Cu etchingCu etching.

8

We would like present today a new promising direction-

resistive electrodes TGEMs

9

The main advantage of these detectors is that they are fully

spark-protected

10

Thick GEM with resistive electrodes (RETGEM)- a fully spark protected detector

A. Di Mauro et al, Presented at the Vienna Conf. on Instrum; to be published in NIM

Geometrical and electrical characteristics:Holes diameter 0.3-0.8 mm, pitch 0.7-1.2 mm,thickness 0.5-2 mm. Resitivity:200-800kΩ/□Kapton type: 100XC10E

30mmor70mm

Principle of operation

11

Filled symbols-single RETGEM, open symbols –double RETGEMsStars-gain measurements with double RETGEM coated with CsI layer.

15 min continues discharge harm ether the detector or the electronics

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

0 1000 2000 3000

Voltage (V)

Gai

n

Ne

Ar

Ar+CO2

QE~30%at λ=120nm

0

200

400

600

1.00E+00 1.00E+02 1.00E+04 1.00E+06 1.00E+08

Rate (Hz/cm2)

Puls

e am

plitu

de (m

V)

Energy resolution ~30%FWHM for 6 keV

With increase of the rate the amplitude drop, but now discharges

Summary of the main preliminary results obtained with kapton RETGEMs

1 mm thick

Fully spark -protected

Discovery:kapton can be coated with CsI and have after high QE

12

Confirmation of high QE

(QE measurements at 185 nm)

13

QE calibration

TMAE filled single-wire gas counter

Double-step RETGEMSwith CsI photocathode

Monochromator Lens

Hg lamp

CsI

Windows

QCsI=QTMAENCsI/NTMAE

14

Hg lamp

Lens

Monochromator

Gas chamberwith RETGEM coated with CsI

Photo of the experimental set up

15

Charge sensitive orcurrent amplifier

-Vdr

Top RETGEM

Bottom RETGEM

V1top

V2 top

Gas in

Gas out

HV feedthrough

Drift mesh

Window

CsI (0.35μm)

Experimental set up for studies RETGEM with CsI photocathodes

UV light

16

TMAE detector

0

100

200

300

400

500

600

700

800

900

1750 1800 1850 1900 1950 2000

Voltage (V)

Counti

ng R

ate

(H

z)

FeFe before

Fe after

UV light

Counting plateau

TMAE detector

Double RETGEM

17

QCsI=33%NCsI/NTMAE~ 14.5%

Hg lamp spectra, measured withTMAE (a) detector and RETGEM (b)

a)

b)

TMAE QE vs. wavelength (c)

c)

(assuming that TMAE is clean enough)18

Measurements of the stability of the RETGEM, using Hg as a source, at 185nm. The light is concentrated on a small slit. About 30min without light have passed between each run.

19

Stability measurements of photosensitive RETGEM

20

Very low single photoelectron counting

rate

Double K- RETGEM with CsI pc

0

20

40

60

0 100 200 300 400

Time (min)

Cou

ntin

g ra

te

Gas gain~ 106

21

Single –electron (CsI pc) counting rate at a constant threshold

Gas gain~ 106

This behavioris similar to RPC

22

“Long –term” stability of CsI pcs measures at low counting rate

K-TGEM, CsI pc#1

0

5

10

15

0 20 40 60 80 100

Time (days)

QE

(%

)

K-TGEM, CsI pc#2

0

5

10

15

20

0 10 20 30 40

Time (days)

QE

(%

)

23

Unexpected problem-very difficult to get the resistive kapton from the US

Dear Mr. Peshkov,

I'm in charge of sales and marketing of Kapton® polyimide film in Europe. As explained in attached notes Kapton® 100XC10E5 is subject to an ITAR license to be exported from the US and this is indeed quite a complex procedure to go through. Suggest you call me at +352 3666 5592 in order to discuss how we can proceed. My best regards,

Giulio Cecchetelli High Performance Films DuPont de Nemours (Luxembourg) S.à r.l.Société à responsabilité limitée au capital de 74.370.250 EuroRue Général PattonL-2984 LuxembourgR.C.S. Luxembourg B 9529

24

Very new (preliminary) results:

RETGEMs manufactured by screen printing technology

For more details see: B. Clark et al., Preprint/Physics/0708.2344, Aug. 2007

25

26

Screen printing is widely used in microelectronics to produce patterns of different shape and resistivity. Therefore, RETGEM technology produced with screen printing techniques offers a convenient and widely available alternative to RETGEMs made of Kapton.

Offers cost-effectiveness, convenience, and easy optimization RETGEMs resistivity and geometry. It is also important to mention that large -area RETGEMs can be produced by this technology.

Advantages of the screen printing technology:

27

Consequent steps in RETGEM manufacturing in by screen printing technique(Oliveira Workshop):

a)

b)

c)

DE-156, an Isola product,

is used as the base material.

Excess copper is removedfrom the top and bottom, thereby creating a copper border.

A resistive paste (Encre MINICO ) is applied to the top and bottom surfaces using screen printing techniques and technology. The paste is cured in air at 200 C for one hour. After the curing process is complete, the resistive layer is 15μm thick.

d)Drill consistently sized holes at even intervals in the region enclosed by thecopper border. 28

RETGEM type- 1 Geometrical and Resistive CharacteristicsThickness = 1mmHole Diameter = 0.5mmPitch = 0.8mmActive Area = 30mm x 30mmResistive Layer Thickness = 15μmResistivity = 1 MΩ/□ or 0.5 MΩ/□

RETGEM type -2 Geometrical and Resistive CharacteristicsThickness = 0.5mmHole Diameter = 0.3mmPitch = 0.7mmActive Area = 30mm x 30mmResistive Layer Thickness = 15μmResistivity = 0.5 MΩ/□

Two types of RETGEM were manufactured by screen printing technology and tested

29

a) medium magnification

Photo of holes at various magnifications:

b) higher magnification

30

Charge sensitive amplifier

-Vdr

RETGEMGas in

Gas out

HV feedthrough

Drift mesh

Radioactive source Window

Experimental set up for studies RETGEM manufactured by screen printing technology

31

Charge sensitive amplifier

-Vdr

Top RETGEM

Bottom RETGEM

V1top

V2 top

Gas in

Gas out

HV feedthrough

Drift mesh

Radioactive source Window

Experimental set up for studies RETGEM manufactured by screen printing technology

32

1.00E+03

1.00E+04

1.00E+05

1.00E+06

200 250 300 350 400

Voltage across RETGEM-2

Gain

Breakdownn

0

2

4

6

8

10

12

14

16

0 200 400 600

Voltage (V)

Sig

nal (V

)

A

B

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1.00E+04

1.00E+05

300 350 400 450 500

Voltage (V)

Gai

n

Results of measurements in Ne (SP-RETGEM type 1)

Gain curve measured with double SP-RETGEM operating in Ne (55Fe).

Gain curve measured withsingle SP-RETGEM (55Fe).

Alpha particles

33

0.1

1

10

100

1000

200 400 600 800 1000 1200 1400 1600

gain

GEM voltage (V)

gain 1

alpha

Fe-55

100

1000

10000

1300 1350 1400 1450 1500 1550 1600 1650 1700

gain

GEM bottom2 (V)

2100V

2300V

2420V

Results obtained in Ar (SP-RETGEM type1)

Single step SP-RETGEM

Double SP-RETGEM

34

100

1000

1620 1640 1660 1680 1700 1720 1740 1760

gain

GEM bottom plate voltage (V)

100

1000

10000

1250 1300 1350 1400 1450 1500 1550 1600

gain

GEM bottom2 (V)

2400V

2500V

2700V2900V

Results obtained in Ar+CO2 (type1)

Single step

Double SP-RETGEM

35

“Low resistivity”(0.5MΩ/□) 1mm thick double step in Ne

(preliminary!)

Double SP-RETGEM, low resistivity in Ne

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1.00E+04

1.00E+05

200 250 300 350 400

Voltage on bottom RETGEM

gain

300V400V

500V

36

The maximum achievable gain with a 0.5 mm thick SP-RETGEM was the same as in the case of the 1 mm thick,

however there voltages were considerably smaller

Some samples had excess of high amplitude spurious pulses

Gain of RETGEM type 2

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

0 200 400 600 800 1000

Voltage (V)

Ga

in

Alphas55Fe

37

Preliminary tests of photosensitive RETGEM manufactured by a screen

printing technology

38

Charge sensitive amplifier

-Vdr

Top RETGEM

Bottom RETGEM

V1top

V2 top

Gas in

Gas out

HV feedthrough

Drift mesh

Window

CsI

Experimental set up for studies RETGEM with CsI photocathodes manufactured by screen printing technology

Hg lamp

Filter

Monochromator

39

QCsI=33%NCsI/NTMAE~ 12.2% - for SP-RETGEM

Hg lamp spectra, measured withTMAE (a) detector and RETGEM (b)

a)

b)

TMAE QE vs. wavelength (c)

c)

SP-RETGEM

-500

0

500

1000

140 190 240 290

Wavelength (nm)

Cou

ntin

g ra

te

(Hz)

Gas gain 3x105

40

SP-RETGEM

0

5

10

15

0 10 20 30 40 50

Time (days)

QE

(%

)

“Long-term” stability

41

Can ~12-14% QE be sufficient for VHMPID?

Volpe talk at this Conference

185 nm

12%

Yes, it looks O’K

(40%-are holes)

42

Preliminary comparison of K- RETGEMs with SP-RETGEMs

▪ In all gases tested K-RETGEMs allow to achieve at least 10 times higher gains than SP-RETGEMs

▪ Some samples of SP-RETGEM exhibit high amplitude spurious pulses (it is not the case for K-TGEMs!)

▪ Both detectors are spark-protected, however after 10 min of continuous glow discharge a low resistivity SP-RETGEM can be damage (it is not the case of K-RETGEM!)-the counting rate of spurious pulses increased

▪ Energy resolution in the case of SP-TGEM was worse

▪ Photosensitive K-RETGEMS and SP RETGEMS have almost the same QE at 185 nm:12-14.5% at 185 nm -and these values remained stable at least in a month scale

43

Conclusions:

●RETGEM detectors are fully spark protected (the energy released in sparks is at least 100 times less than in the case of metallic TGEMs)

● At low rate they behave like GEM ( and the gas gain is stable with time) and at high rates and high gains RETGEMs are more resembling RPCs ( gain reduces with rate)

● Being coated by a CsI layer RETGEMs operate stable at high gains and low rates and their QE is 10-14.5% at 185nm

●“Long term “ (few months) stability of RETGEMs with CsI pc was demonstrated

● We believe that RETGEMs can be good candidates for the VHPMID and some other RICH detectors

44

Future tasks:

In contrast to K-TGEMs, the SP-RETGEMs require more tuning up:●optimization its resistivity and geometry,● understanding some detail in operation, ● tests in C5H12 gas

Final evaluation and conclusions can be drowned only after a beam test

45

2

3

4

5

1

Pad plain

RETGEMs

CsI

Drift mesh

Should bemanufactured

New,exists

Old,exist

Should bemodified

40 mm

Old,exist

Proto-4

Plans for future beam test

Liquid radiator46

The photodetectors to be tested :

GEM

TGEM

RETGEM

The beam test will allow to select the best one

47

Spairs

Wire chamber with CaF2

window approach is not excluded yet!

Optimization of the RPC electrodes resistivity for high rate applications

P. Fonte et al., NIM A413,1999,154

TMAE detector cross checks

Counting rate measurements from TMAE detector as function of radius

Efficiency scan

0

200

400

-20 -10 0 10 20

Distance from the center (mm)

Cou

ntin

g ra

te

(Hz)

Ionization chamber check

(with a 185 nm filter)

Charge sensitive amplifier

-V

RETGEMGas in

Gas out

HV feedthrough

Drift mesh

Window

Current measurements:

CsI

Hg lamp

Filter

A

Ionization chamber check(with a 185 nm filter)

0

10

20

30

40

0 200 400 600 800

Voltage (V)

Cur

rent

(pic

o A

)

TMAE detector

RETGEM, Ne

Backdiffusion

Ne

0.01

1

100

10000

0 200 400 600 800

Series1

Series2

CO2

0

10

20

30

40

0 1000 2000 3000

Series1

Series2

Ar+25%CO2 my Kethley

0

100200

300

400

0 500 1000 1500 2000

Series1

Series2

Active area

r

R

Π(1+3)r2/πR2==0.25/0.64=40%

Giacomo related slides

Gas Cherenkov detectors for high momentum Gas Cherenkov detectors for high momentum charged particle identification in thecharged particle identification in the

ALICE experiment at LHCALICE experiment at LHC

G. Volpe, D. Di Bari, E. Garcia, A. Di Mauro, E. Nappi, P. Martinengo, V. Peskov, G. Paic,

K. A. Shileev, N. Smirnov

6th International Workshop on Ring Imaging Cherenkov Counters

15-20 October, Trieste

A talk presented by G. Volpe yesterday

pioni

pioni

HMPIDRICH , PID @ high pT

HMPIDRICH , PID @ high pT

ITSVertexing, low pt tracking and PID with dE/dx

ITSVertexing, low pt tracking and PID with dE/dx

TPCMain Tracking, PID with dE/dx

TPCMain Tracking, PID with dE/dx

TRDElectron ID,Tracking

TRDElectron ID,Tracking TOF

PID @ intermediate pT

TOFPID @ intermediate pT

PHOS,0 -ID PHOS,0 -ID

MUON -ID

MUON -ID

+ T0,V0, PMD,FMD and ZDC Forward rapidity region

+ T0,V0, PMD,FMD and ZDC Forward rapidity region

L3 Magnet B=0.2-0.5 TL3 Magnet B=0.2-0.5 T

ALICE experimentEMCal

ALICE is designed to study the physics of strongly interacting matter and the quark-gluon plasma (QGP) in nucleus-nucleus collisions at the LHC. The p-p physics will be study as well as reference data for the nucleus-nucleus analysis.

High energy

How it was designed How it is looked just before the installation

ALICE RICH is installed inside the magnet and is in a commissioning phase now.We are looking forward for the first physics results!

ALICE RICH

~ 2m

ALICE Club - May 2, 2005Paolo Martinengo

Example of a single radiator threshold imaging Cherenkov

A. Braem, C.W. Fabjan et al., NIM A409, 1998, 426

Nikolai Smirnov, Yale University

Y

Z

X

50 cm

50 cm

AeroGel, 10cm

UV Mirror, spherical shape in ZY

Double sided read-out plane:planar detectors with CsI

CaF2 Window

C4F10 gas

CF4 gas

Particle track & UV photons

R position: 500 cm.Bz: 0.5 T

Another idea…

Blob diameter for C4F10, pad size = 0.8x0.8 cm2

VHMPID volumes

VHMPIDRadiator gas options:

• CF4 (n ≈ 1.0005, th ≈ 31.6) has the drawback to produce scintillation photons (Nph ≈ 1200/MeV), that increase the background.

• C4F10 (n ≈ 1.0014, th ≈ 18.9) is no more commercially available.

• C5F12 (n ≈ 1.002, th ≈ 15.84) has been chosen.

Photon detector options:

• Pad-segmented CsI photocathode is combined with a MWPC with the same structure and characteristic of that used in the HMPID detector.

• The gas used is CH4, the pads size is 0.8×0.84 cm2 (wire pitch 4.2 mm), and the single electron pulse height is of 34 ADC channels.

• The chamber is separated from the radiator by a CaF2 window (4 mm of thickness).

• The other option for the photon detector could be a GEM-like detector combinedwith a CsI photocathode (higher gain, photons feedback suppression).

(see G. Volpe talk at this Conference)

Photodetector

Charged particle

Mirror

120 cm

Radiator vessel

•In the case of focusing setup the determination of emission Cherenkov angle is possible.

• Pattern recognition algorithm is needed to retrieve the emission angle.

• A back-tracing algorithm has been implemented to retrieve the Cherenkov emission angle. It calculates the angle starting from the photon hit point coordinates, on the photon detector.

Study of the detector response for the focusing setup

(from G. Volpe talk at this Conference).

K

p

Kp

p115 < p < 30 GeV/c

p0

K1

K, p0

12.5< p < 8 GeV/c

?0< 2.5 GeV/c

Particle Id.C5F12

8 < p < 15 GeV/c

2.5 < p < 8 GeV/c

8 < p < 15 GeV/c

Momentum

Simulation results: Cherenkov angle

from G. Volpe talk at this Conference

The points and the bars in the plot correspond to mean and RMS of a sample of 100 events, respectively