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 universality (g NN =g N  =g  ) g’  affect Critical Density of Pion Condensation property of high density nuclear matter g’ 

pion, charged particle Detector Requirement Motivation –Tracking of low energy (< few hundred MeV) charged particle Requirements ( why GEM? ) –high position and angle resolution spatial : <100  m & angle: < 2 mrad –rate capability : >100kcps –can be operated under high magnetic field: < 1 Tesla –boundary condition ~ narrow space neutron 70m TOF TOF counter (NPOL2) 10 cm  cm 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 m 3 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 mm 3 –2 plastic scintillators –Fine Mesh PMT ~ gain is 10 5 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 : 100  m (designed value) –radiation tolerance –tolerance for magnetic field: ~1 Tesla 1 st Plane 2 nd Plane Electronics Cable (analog sig.) 77mm 452mm 110mm cathode 3mm 1mm 1.5mm Readout Board GEM1 GEM2 GEM3 H.V.

GEM CERN-GEM (supplied by GDD group) –Active Area: 307.2x50 mm –Segmented by two area protection from discharge –Standard Material & Size Cu-PI-Cu  m hole 70  m, pitch 140  m GEM holes (standard) triangular pattern size: 70um pitch: 140um cross section 200  m separation H.V. the measured amplification factor in each gas.

Readout Board and Connector Readout Board –Same size with GEM –Base : G10 50  m –Cu-PI-Cu :  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 400  m 340  m 80  m

Readout Electronics Analog-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 x2 out x2 SW-VME x4 memory to/from neutron DAQ Trigger CPLD Trigger Sci. 2ch data / control trig hold from GEM

Experiment (1) Date: July 2006 Reaction: 12 C(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: 12 C(p,n  + ) 12 C(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

12 C Target proton beam neutron pion 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