Development of a Vertex Chamber with using GEM Yutaka Mizoi Osaka Electro-Communication University Colleagues; Tomokazu Fukuda, Shizu Minami, and Wataru Imoto Workshop for MPGD at Kyoto University, 2004.Dec.3-4.

Contents 1) Experiments 2) Cylindrical Drift Chamber System 3) Design of Vertex Chamber 4) Schedule and etc. 5) Other Cylindrical GEM Detectors

1) Experiments I) Study of Double-  J-PARC a) Confirm the existence of 4 H b) Search for 5 H II) p + n p + RCNP  p +   High vertex resolution is required for tracing two-  tracks. High counting rate from background.

2) Cylindrical Drift Chamber System (CDS) Vertex Chamber Cylindrical Drift Chamber Hodoscopes Solenoid Magnet k- k+  Vertex Determination Momentum Analysis Particle Identification

3) Design of Vertex Chamber Development History in 1998: Previous CDS designed by J. P. Nakano, et al. for  experiments. No Vertex Chamber, Z-Chamber outer of CDC did not be used due to... accepted in 2002: A newly developed vertex chamber will be installed in the previous CDS, but Recently, design study of a new CDS has been started for J-PARC.

E961 E906 Target (density) LiH (0.83 g/cm 3 ) 9 Be (1.85 g/cm 3 ) Target size 5.08x1.225x20 cm x1.225x15.24 cm 3 Target position(0, 0, 27.3) cm(0, 0, 0) CDS acceptance 62% of 4  55% of 4  (60  <  <146  ) (71%) K + acceptance 69 msr 29 msr * ZZ 0.8 mm rms 3 mm rms pp 2.4 MeV/c rms 4.3 MeV/c rms * The upper 4 elements of FP were excluded from trigger in E906. Results of GEANT simulations Hotchi

w/o vertex chamber w/ vertex chamber  decays Double  signals Distance of Closest Approach (cm) DCA<2cmDCA<0.8cm Hotchi

Required dimension : ~  100 mm x 315 mm New z-vertex chamber

Two Promising Designs - Anode wire or GEM ? Read-out Strip Electrode Anode Wire Field Wire GEM foil x 2~3 -- -- Anode Strip Z position Strip GEM Z R Anode-wire configuration; Well known structure, One-dimensional tracking, Wire-tension stress... GEM-foil configuration; Two-dimensional tracking, No mechanical Stress, High counting rate, Unknown structure, Mass density (Inner or Outer is another option.)

Design of the Read-out Strip-Electrode Sheet Polyimide 25  m+Cu 18  m X 3 layers, 3mmX129.3mm Strip with 0.2mm gap X 96 strips

Required Design for GEM i) Gas gain ? 10 3~4 ~ achievable with single GEM foil. ii) Multi GEM ? for safety margin; two or three GEMs, but thickness is another problem. iii) Size ? 30cm X 15cm ~ available in CERN workshop.

4) Development Schedule 1) Anode-wire configuration Test in a planer geometry will start soon. A test bench with anode wires will be ready at KEK in December. Thanks for Sekimoto-san. 2) GEM-foil configuration Three 10cm 2 -GEM foils made in CERN have just arrived. A test bench in a planer geometry is now under designing. Prof. Sauli gave us a large-area (junk) GEM foil with 31cmX31cm. A mechanical test for forming a GEM foil into cylindrical shape will be performed in this FY.

5) Other Cylindrical GEM Detectors I) BoNuS Lab. Howard Fenker, et al. BoNuS=Barely off shell Nuclear Structure Radial TPC 20cm x 8-12cm 

II) Pierre-André Amaudruz, et al. TACTIC=TRIUMF Annular Chamber for Tracking Identification of Charged particles Nuclear-Astrophysical Reactions

Summary Which is better for the present purpose, GEM or Anode-wire configuration? We will continue study to resolve it. Anyway, we will develop a cylindrical GEM detector. It is a very attractive challenge itself. A CDC will be replaced by a cylindrical GEM TPC !?