Development of Tracking Detector with GEM

Kunihiro Fujita RCNP, Osaka Univ.Yasuhiro Sakemi 　 CYRIC, Tohoku Univ.

Masaharu Nomachi Dep. of Phys. , Osaka Univ.

• Short range component of Nuclear force: g’– ++g’ model

• Landau-Migdal parameters: g’ (g’NN, g’N, g’)– g’ : Few experimental information

• Coherent pion production is sensitive to g’

Physics Motivation

),q(eff V ),(),( qq VV LMV

universality(gNN=gN=g)

g’ affect • Critical Density of Pion Condensation• property of high density nuclear matter

g’

n

p

t

Initial state Intermediate state Final state

“Absorb” the virtual pion(off-shell pion)

“Emit” the real pion(on-shell pion)

Propagation of -h states

RecoilHe3 He3

Virtual Pion : +*

~ interaction (w,q)

Ground State

is generated sequentially

pion, charged particle

Detector Requirement• Motivation

– Tracking of low energy (< few hundred MeV) charged particle

• Requirements ( why GEM? )– high position and angle resolution

• spatial : <100m & angle: < 2 mrad– rate capability : >100kcps– can be operated under high magnetic field: < 1 Tesla– boundary condition ~ narrow space

neutron70m TOF

TOF counter (NPOL2)

10 cmcm

Magnet & Counter Box

400 MeV proton from Ring cyclo.

Swinger Magnet (proton is bent by 90 deg)

B~1.5T

Detectors

• Size : 1×1×0.1 m3

• 4 liquid, 2 plastic scintillators with charged particle catcher

• Energy resolution : 500 keV• Detection efficiency : 15 %

• Flight Path was set to 70m• Developed by Tokyo Univ. group

• Gas Electron Multiplier (GEM) detector　~ Tracking

newly developed for this experiment

• Plastic Scintillator ~ Trigger– Size : 320×50×10 mm3

– 2 plastic scintillators– Fine Mesh PMT ~ gain is 105 at 1 Tesla

Trigger counter

typical

Tracking counter

Neutron Counter (NPOL2)

Pion Counter

Detector specification• To Get position information for Two layers• Component

– Cascade GEM structure ~ Three layers– Two dimensional Readout Board– Charge Information : Multi channel ADC

• Specification – high position resolution

: 100m (designed value)– radiation tolerance – tolerance for magnetic field: ~1 Tesla

1st Plane

2nd Plane

Electronics

Cable (analog sig.)

77mm452mm

110mm

cathode

3mm

1mm

1mm

1.5mm

Readout Board

GEM1

GEM2

GEM3

H.V.

GEM

50307.2

• CERN-GEM (supplied by GDD group)

– Active Area: 307.2x50 mm– Segmented by two area

• protection from discharge

– Standard Material & Size • Cu-PI-Cu 5-50-5m• hole 70m, pitch 140m

GEM holes (standard)triangular pattern

size: 70umpitch: 140um cross section

200m separation

H.V.

Triple GEM effective gain

1.E+02

1.E+03

1.E+04

1.E+05

340 350 360 370 380 390 400 410ΔVgem

Effective Gain

ArCO2

ArC4H10

the measured amplification factor in each gas.

Readout Board and Connector

• Readout Board– Same size with GEM– Base : G10 50m– Cu-PI-Cu : 5-25-5 m– Strip width

• horizontal (x) : 80 m• vertical (y) : 340 m

– pitch: 400 m

• Connection– Flexible Cable– Sandwiched Structure :

GND-Signal-GND

Readout Board (supplied by ‘RAYTECH, INC.’)

Flex Cable (supplied by ‘TAIYO Ind. CO., LTD’)

768ch

120ch

connect 400m

340m

80m

Readout Electronics

Readout ElectronicsAnalog-LSI boards

Readout Board

FPC (one of 14)

to VME module

Va32_Rich2

~2000ch

I/O Board

Space Wire Protocol

Analog MUX

Trig/Ctrl

data

CPLD

Flash ADC

• Analog– VA: amp, sample/hold, serialize– TA: shaper, discriminator trigger– Dynamic range : ~ 140 fC– 256ch outputs are multiplexed

• Digital– ADC: 12-bit– Serial Data Transfer (LVDS)– Sparse Data Scan : Skip un-triggered

chip

• Data Transfer Rate – ≳ 2kHz limited by FADC

to VME

Data Acquisition• SW-VME module

– transceiver( ADC data, control commands)

– decoder– memory control

• Trigger module– decide coincidence level GEM, Trigger SCI, and neutron counter

FPGA GDG

VME bus

x8

in x2out x2

SW-VME x4

memory to/from neutron DAQ

TriggerCPLD

Trigger Sci.2ch

data /control

trighold

from GEM

Experiment (1)

• Date: July 2006• Reaction: 12C(p,p’), faint beam (direct)• Beam:

– particle: proton– energy: 392MeV– rate : <2k count / sec

• Detector Setting– Gas : Ar/CO2 (7:3)– Vgem : ~ 410V (gain ~12k)

proton

GEM

Spectrometer (Grand Raiden)

proton

trigger counter

GEM

Result(1)• Position Dependence of GAIN

– uniformity was was 2%(RMS) for x1, and x2 3~5% for y1, and y2

• Angle Dependence of Cluster Size (CLS)– at 0 deg. cls ~ 3, 4 – at 40 deg. cls > 10

Fig1. position dependence of gain

=0 deg.

=40 deg.

Tracking Result

beam position with three magnetic field settings.

FWHM:~2mm (= 200 keV)

[mm]

•Tracking information was observed ~ peak width was 2mm (include beam size)

Experiment(2)

• Date: October and November 2007• Reaction: 12C(p,n+)12C(g.s.)• Beam:

– particle: proton– energy: 20MeV, 392MeV– rate : <2k count/sec (pion counter)

• Detector Setting– installed in the high Magnetic field

~1 Tesla– GEM + trigger SCI + neutron counter

proton

+neutron

12C Target

proton beam

neutronpion counter

50cm

Swinger Magnet

Result(2)

• Gain dependence in Magnetic field– measured with 3 settings 1.1, 0.98, and 0.75T– fluctuations was less than 3%

• position resolution– 2.3mm (FWHM)

peak position for each B

ADC

FWHM:~2.3mm

SUMMARY• We developed GEM detector for nuclear experiment.• Large size GEM and Two dimensional Readout Board

is made.• Readout Electronics was developed with VA/TA

chip, FADC board, SW-VME and CPLD module.• Beam test was performed and specification was

estimated.• Data run was performed and position information

was acquired successfully in the high magnetic field.

Next Plan• improve DAQ system for the high counting rate• Data analysis with GEM + neutron counter

Missing Mass Spectrum