1

Development of a new generation of micropattern gaseous detectors for

high energy physics, astrophysics and medical applications

A.Di Mauro,1 P. Fonte2, P. Martinengo1, E.,Nappi3, R. Oliveira1, V. Peskov1, P. Pietropaolo4, P. Picchi5

1CERN, Geneva, Switzerland2 LIP/ISEK Coimbra, Portugal

3INFN Bari, Italy4INFN Padova, Italy5INFN Frascati, Italy

2

In the last two decades very fast developments happened in the filed of gaseous detectors of photons and particles. Traditional gases detectors: wire–type and parallel plate-type (RPCs) -which are widely used in high

energy and astrophysics experiments have now serious competitors: Micropattern Gaseous Detectors

(MPGDs)

Due to the importance of these developments an RD 51collaboration was formed a CERN

The aim of this collaboration is to coordinate affords from various groups working on MPGDs

3

1) Strip typeExample: Microstrip gas counters (MSGCs)A. Oed, NIM A263, 1988, 351

Examples:CAT/WELL, Gas Electron multiplier (GEM)A.Del Guerra et al., NIM A257, 1987,609M. Lemonnier et al., Patent FR 2727525 , 1994F. Sauli, NIM,A386,1997,531

3) Parallel-plate typeExample: Micromesh gas chamber (MICROMEGAS)Y. Giomataris et al., NIM A376, 1996, 29

4) Hole type

Glass substrate

There are four main designs of micropattern gaseous detectors:

CAT/WELLGEM

Anodes

~100μm2) MicrodotS.Biagi et al., NIMA392, 1997, 131

4

The main advantage of MPGDs is that they are manufactured by means of microelectronics

technology, which offers high granularity and consequently an excellent position resolution.

Due to their advantages the MPGDs cangue more and more applications. In high energy physics they were already successfully used in:Hera-B, COMPASS TOTEM, LHC B etc.

Their use in CMS, ATLAS ALICE and in some other experiments under consideration

5

However, the fine structure of their electrodes and the small gap between them make MPGDs electrically “weak.” In fact, their maximum achievable gain is

usually not very high, compared to traditional detectors, and without special precautions they can be easily destroyed by sparks, which may occur during their

operation

(which is not the case of traditional detectors: wire and parallel-plate type)

6See, for example G. Charles et al., NIM A648, 2011, 174

.. and sparks, unfortunately, in experiments are practically unavoidable

7

There are several methods of protecting micropattern detectors and FEE from destruction: segmentation of electrodes on smaller parts, protective diodes…These methods were successfully implemented in the case of GEM and in some MICROMEGAS designs

Alternative approach, which becomes more and more frequent inside the

RD51collaboration, is the useresistive electrodes.

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The first micropattern detector with resistive electrodes was GEM, and later this approach was also applied to other

detectors: MICROMEGAS and CAT (all had unsegmented electrodes)

Res. GEMOliveir at al., NIM A576, 2007, 362

Res. CATA.Di Mauro et al., IEEE Nucl. Sci Conf Rec, 6, 2006,3852

Res. meshR.Oliveira etal., IEEE Nucl. Sci57,2010, 3744

Res. MICROMEGASR.Oliveira etal., IEEE Nucl. Sci57,2010, 3744

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They were hybrids layout between GEM and RPC

The principle of operation of RPC: discharge energy is quenched because of the resistivity of electrodes

-V

Resistiveelectrodes

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This study triggered a sequence of similar developments, which are nowadays pursued not only by our group, but by several other groups in the frame

work of CERN RD51 collaboration

See recent reports at the 2nd Intern. Conf. on Micro Pattern Gaseous Detectors, August 2011, Kobe, Japan (to be published in JINST)(http://ppwww.phys.sci.kobeu.ac.jp/%7Eupic/mpgd2011/abstracts.pdf)

A couple of examples of main developments will be given below:

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See for example: a photo of RETGEM

from: R. Akimoto et al,presentation at 1st

MPGDs conference in Crete,2009

or

Several groups (mostlyJapanese) are now successfullydeveloping various designs ofRETGEMs

Spark protected RETGEMs and Res. CAT:

Res. CAT developed by Breskin groupL. Arazi et al., JINST 7 C05011, 2012

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Advantages: 1. More suitable for large-area detectors2. Better fit requirements for position measurements 3.Flexible in design implementation4. In some designs offer better rate characteristics

Tested configurations:

1) Resistive strips without intermediate layer between the strips and the metal readout strip(see for example V. Peskov et al., NIM, A610 2009 169)

2) Res. electrode strips with a thin FR-4 glue intermediate layer(R. Oliveura et al., NIM,A576,2007,362)

3) Resistive strips with a thick FR-intermediate layer (T. Alexopoulos et al NIM A 640, 2011, 110)

Today we would like to presenta new approach:resistive electrodes segmented on stripswith a network of metallic readout strips located under the resistive grid

1)

2)

3)

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As was shown in the previous slide, first we applied this new technology to resistive GEMs (~2009).

In the last couple of years (2010-2012) we extended this approach to all other main micropattern designs.

Below are examples of only three of such detectors.We choose them because they are oriented towards applications in which some members of our team are currently involved:

1.RICH,2.Dual-phase noble liquid TPCs, 3. X/gamma ray imaging deices

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1. Resistive microstrip detector

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PCB with 5μm thick Cu layer on thetop and two layers of readout strips (oriented perpendicularly) on the bottom

Milled grooved 100 μm deep and0.6 μm wide, pitch 1mm.

The grooves were then filled with resistive paste (ELECTRA Polymers)

By a photolithographic technology Cu 20 μm wide strips were created between the grooves

0.6mm

1mm

20μm

a)

b)

c)

d)

0.5mm

e)Finally the entire detector was glued on a supporting FR-4 plate

0.2mm 0.1mm

0.5-1mm

Cathode res. strips

Anode strips

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Connections toX pick up strips

Connections toY pick up strips

Anode strips

Cathode resistivestrips

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Gas gains

Pos. resol. measurements Rate characteristics

Runs #12-17

0

200

400

600

800

1000

1200

0 200 400 600 800 1000 1200

Actual position ( micr)

Mea

sure

d p

osi

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r)

~200μm

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2. Resistive microdot-microhole detector

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a)

Multilayer PCB with Cu layers on the top and bottom and with the inner layer with readout strips

Upper Cu layer etching

The remaining grooves were then filled with resistive paste (ELECTRA Polymers)

Removal of the Cu

v

v

v

v

Filling withCoverlay with“dot” opening

b)

c)

d)

e)

v

v

Resistive anode dotsResistive cathode strips

Readout strips

1mm 0.1mm

Holes

0.1mm

Manufacturing steps:

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Magnified photograph

Schematic drawing and a principle of operation of res. microdot detector(resembling MHC, see:J. Maia et al., IEEE Trans. Nucl. Sci 49, 2002, 875)

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Gas gain vs. the voltage of R-Microdot measured in Ne and Ne+1.5%CH4 with alpha particles (filled triangles and squares) and with 55Fe (empty triangles and squares).

0.1

1

10

100

1000

10000

100000

1000000

0 200 400 600 800

Volateg (V)

Gai

n

Ne

Ne+1.5%CO2

Gain (triangles) dependence on voltage applied to R-Microdotmeasured in Ar (blue symbols) and Ar+1.6%CH4 (red symbols)and in Ar+9%CO2. Filled triangles and squares –measurements performed with alpha particles, open symbols - 55Fe.

0.1

1

10

100

1000

10000

100000

1000000

0 200 400 600 800 1000

Voltage (V)

Gain

Ar

Ar+1.6%CO2

Ar+9%CO2

Interesting feature: at high gains operates in self-quenched streamer mode

In all gases tested the maximum gains achieved with the R-Microdot detectors were 3-10 time higher than with R-MSGCs

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3. Resistive microgap-microstrip detector

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a)

Multilayer PCB with a Cu layer on the top and one layer of readout strips on the bottom, 0.5 pitch

Upper Cu layer etching

The grooves were then filled with resistive paste (ELECTRA Polymers)

Removal of the Cu

v

If necessary, filling withCoverlay (an option)

b)

c)

d)

e)

M-M- RPC manufacturing steps:

Resistive strips

Readout strips

0.5 mm 0.2mm

v

0.035mm

0.1mm

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A

B

C

Contact pad

Contactpad

Resistive strips

Total resistivity ofthe zone B 500MΩ(adjustable) Resistivity of zones A and C500MΩ (adjustable)

Surface resistivity100kΩ/□ (can beadjusted to exper.needs)

Top view:

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This plate is in fact a reproduction of the resistive MICROMEGAS anode board

(see the following talks)

The idea is to assemble from these plates a parallel- plate detector (M-M-

RPC), so that the cathode metallic mesh is not used

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Orthogonalresistive strips

Inner signal strips

Artistic view of the M-M RPC

PCB sheet

From these plates RPC were assembled with gaps ether 0.5 or 0.18mm

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An option with pillars (similar to MICROMEGAS)

PillarsRes. strips

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A fundamental difference between “classical “ RPC and M-M- RPC

Film resistor

M-M-RPC offers high2D position resolutions (with orthogonal strip or various stereo strip arrangements to avoid ambiguity) and have potential for good timing properties

Usual RPC

M-M-RPC

“Signal”electrodesCurrent

Orthogonalresistive strips

Current

500MΩ

Inner signal strips

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Gain estimation in an RPC geometry:

CsI layerUV

X-raysFe anode

0.5mm

0.1-0.2mm

Photoelectron tracks

(Due to the time constrains the CsI coating was done by a spray technique)

A=expαx

x

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M-M-RPC with spacers in corners

The highest gains were obtained with resistive micropattern detectors

Estimated gain, preiminary

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

0 500 1000 1500 2000

Voltage (V)

Gain

Ar+10%ethnan0.5 mme,

X-rays and UV

Ar+25%CO2UV, 0.18mm

Ar+25%CO2X-rays

00.20.40.60.8

11.2

1 100 10000 1000000

Counting rate (Hz/mm 2)

Mea

n si

gnal

am

plitu

de

(arb

. uni

ts)

Typical rate response

(combined current and pulsed measurements)

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Now shortly about the applications in which our team

is involved

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1. RICH(recent results)

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The VHMPID should be able to identify, on a track-by- track basis, protons enabling to study the leading particles composition in jets (correlated with the π0 and /or γ

energies deposited in the electromagnetic calorimeter).

There is a proposal (LoI) to upgrade ALICE RICH detector in order to extend the particle identification for hadrons up to 30GeV/c. It is called VHMPID.

(HMPID)

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The suggested detector will consist of a gaseous radiator (for

example, CF4 orC4F10 ) and a planar gaseous photodetector

The key element of the VHMPIDis a planar photodetector

C4F10

For details see a talk at this conference: DI MAURO, Antonello (CERN) R&D for the high momentum particle identification upgrade detector for ALICE at LHC

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Our previous prototype (very successful!)

Triple res. GEM with metallic strips

P. Martinengo, V. Peskov, et al., NIM, 639,2011,126V. Peskov et all.,arXiv:1107.4314 (2011) 1-7

RE

HMPID readout electronics

Cherenkov light was detected

(For more details see A.Di Mauro talk)

MIP

Cherenkov ring

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RETGEMcoated with CsI

R-MSGCor R-MICRODOT

Main advantages:Two times less elements,Less voltages,Very high gain (an important safety factor)

Concerns:Aging (to be studied)

New prototype (recently tested)

1.E-011.E+001.E+011.E+021.E+031.E+041.E+051.E+06

0 200 400 600 800 1000

Voltage (V)

Gai

n

1

10100

FW

HM

(%

)

R-MSGC

R-MSGC+Cs-IRETGEM

Pilot studies:(while LoI was written and circulated)

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Inject EF and sealed when the signal was close to maximum

0

0.2

0.4

0.6

0.8

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1.2

0 100 200 300 400 500 600

Time (min)

Sig

nal

(V

)

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1.2

0 200 400 600 800

Time (min)

Sig

nal

(V

)

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Time (min)

Am

pli

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)

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0 100 200 300 400 500 600 700

Time (min)

Sig

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(V

)

Tests with EF vapors

Ist day 2d day

QE enhancement (after correction) is about 50%; work is still going on)

Preliminary

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2.A new double-phase detector(work in progress)

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The concept of usual double phase noble liquid dark matter detectors

Two parallel mesheswhere the secondary scintillation light is produced

Primary scintillation light

From the ratio ofprimary/secondarylights one canconclude about thenature of the interaction

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Several groups are trying to develop designs with reduced number of PMs(there was work from Novosibirsk group, we made sealed gaseous PMs, Breskin group is working on sealed gaseous PMs ..)

In E. Aprile XENON: a 1-ton Liquid Xenon Experiment for Dark Matterhttp://xenon.astro.columbia.edu/presentations.htmlIt was suggested to use CsI photocathode immersed inside the noble liquid

Large amount of PMs in thecase of the large-volume detectorsignificantly increase its cost

(Another option for the LXe TPC, which is currently under the study in our group, is to use LXe doped with low ionization potential substances (TMPD and cetera).

One large lowcost “PM”

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This suggestion was based on ourearly studies which we made togetherwith Aprile’s team

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However, this concept was never materialized in any

detector…

To verify feasibility of this approach we made some preliminary tests

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CsI photocathode

grids

PM

10 cmAlpha source

Ar gas

LAr

Experimental setup(ICARUS cryostat combinedwith a purification system)

Ar gas, room temper., 1 atm

LAr+ gas phase

V. Peskov, P. Pietropaolo, P. Pchhi, H. Schindler

ICARUS group

Performance of dual phase XeTPC with CsI photocathode and PMTs readout for the scintillation lightAprile, E.; Giboni, K.L.; Kamat, S.; Majewski, P.; Ni, K.; Singh, B.KetalDielectric Liquids, 2005. ICDL 2005. 2005 IEEE International Conference Publication Year: 2005 , 345 - 348

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EventCharge

hvhv

R-Microdot

CsI photocathode

Shielding RETGEMs(with HV gatingcapability)

LXe

Photodetectors?? (if microdot gain is insufficient)

Anodes Resistive cathodesMultiplication region

The possible way to suppress the feedback

In hybrid R-MSGC, the amplification region will be geometrically shielded from the CsI photocathode (or from the doped LXe) and accordingly the feedback will be reduced

45

Results obtainedwith alphas and 55Fe

Measurements in Ar at room and cryogenic temperatures (preliminary)

“streamer”mode

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 100 200 300

Time (min)

Sign

al a

mpl

itud

e (a

rb. u

nits

)

Stability with time

No feedback pulses were observed

105-115K

300K

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3. Micrpstrip-microgap for imaging applications

(Work just started)

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Scanners:

30% efficiency for 400 keVat shallow angle

b) Gamma ray

a) X-ray (edge on)

T. Francke et al.,NIM A508, 2003, 83

T. Francke et al.,NIM A471, 2001, 85

I. Dorion et al., IEEE Nucl, Sci., 34. 1987,442Contacts with industry are established;they already evaluate our prototypes

Pos. resol.50μm in digitalform, rate 105Hz/strip

Tantalumconvertor

48

Another goal was/is to combinehigh pos. resolution with high time resolution.

First step in this direction was already successfully done by Fonte et al(see Proc. of Science, RPC 2012, 081).

Besides the particle detections another application is TOF- PET on which Fonte group is actively working

Bidimentional position resolution 70μmin with combination 80 ps timing

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Above only three examples of applications in which members of our

team are currently working were given

In reality much more work is going on

restive strip micropattern detectors.

A few more examples:

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1) Res. TGEM with metallic strips for environmental and safety applications(CERN-KTT project)

(this project is in a final stage, ready for commercialization)

Prototype of a flame detectorSensitivity 100 higher any commercial detector

Prototype of Rn detectorSensitivity is equal to commercial Rn detectorsOperating in on line mode, but ~50 times cheaper

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2) A.Ochi et al., Resistive strips microdot detector

Presented 10th RD51 collaboration meeting, October 2012

3) D. Attie et al., A piggyback resistive Micromegas

Presented at the RD51 meeting, December 2012

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Resistive MICROMEGASis planned to be also used insome other applications, for example environmental (muon tomography of undergroundwater reservoir),

4) However, the most remarkable example is MICROMEGAS for ATLAS upgrade

P. Salin, Presenation at the RD51 meeting, december2012

…see also today presentations

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Conclusions:1) A new generation of micropattern gaseous detectors with

resistive-strip electrodes combined with metallic 2D readout strips was developed. They offer excellent position resolution and are spark protected

2) We try to implement these detectors in several applications:RICH,

Noble liquid TPC, Scanner/medical,

environmental/security

3) A similar approach was in parallel developed by MAMMA collaboration and resistive strip MICROMEGAS will be employed in the ATLAS small wheel. More developments are in progress

4) Of course, these detectors have limited rate capabilities and this can be an issue in high rate environment, however some improvements in their rate characteristics still are possible

In progress

In a final stage

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Back up slides

55

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Optimization of the RPC electrodes resistivity for high rate applications

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

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ATLAS R-MICROMEGAS characteristics

T. Alexopoulos et al., NIM A640, 2011,110

103Hz/mm2

(2-3)104

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The concept of this detector is resembling the so called MHCP detector , however the important differences were that it was

manufactured from a printed circuit plate 0.4 mm and had resistive cathode strips making it spark-protective.

J.M. Maia et al., NIM A504,2003, 364

Anode stripsCathode strips

Holes

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Images with strip RETGEM

60

00.20.40.60.8

11.2

1 100 10000 1000000

Counting rate (Hz/mm 2)

Me

an

sig

na

l am

plit

ud

e

(arb

. un

its

)

Rate response (MSGC):

The gas gain variations with counting rate. Measurements were performed in Ne+10%CO2 at gas gain of 5103

(signal drop at counting rate >103Hz/mm2 is due to the PCB board surface charging up, but not due to the voltage drop on resistive strips)

103

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Physics behind this phenomena

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Results of measurements induced signals profile from the readout strip oriented along(green curve with crosses) and perpendicular to the anode strips of R-MSGCs (rhombuses, triangles and squares). Rhombus- the collimator is aligned along the strip #0. Triangles -the collimator was moved on 200μm towards the strip#1. Squares- the collimator was aligned between the strip#0 and # 1. Measurements were

performed in Ar+10%CO2 at a gas gain of 5x103.

Preliminary results of measuremenst the induced signals on the strips:

More precisely the positionresolution will be determinedduring the oncoming beam test

Runs #3-6

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0.5

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1.5

-5 -4 -3 -2 -1 0 1 2 3 4 5

Readout strip number

Mea

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(ar

b.

un

its)

Runs #12-17

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Actual position ( micr)

Mea

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mic

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Profiles of signals induced on pick up strips(0.3mm wide collimator)

Correlation between the measured and actual position of the collimator

Expected

Measured

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Gas gains

Pos. resol. measurements Rate characteristicsRuns #12-17

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1200

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The main detectors on which RD-51 is focused

All of them can be done resistive, hence spark protected

Micromegas GEM TGEM

Micrpixel MHSC Ingrid