1. Development of an active target for astrophysical experiments at CRIB Takashi Hashimoto The University of Tokyo, CNS

2. Collaborators Center for Nuclear Study (CNS), The University of Tokyo T. Hashimoto*, S. Kubono*, H. Yamaguchi*, D. N. Binh, S. Hayakawa, D. M. Kahl S. Ota*, S. Michimasa*, T. Gunji*, R. Akimoto*, H. Tokieda*, T. Uesaka*, H. Hamagaki* (*: active target development team at CNS) Institute of Particle and Nuclear Study (IPNS), High Energy Accelerator Organization (KEK) H. Ishiyama, H. Miyatake, W. X. Watanabe, Y. Hirayama, N. Imai, S. C. Jeong University of Tsukuba K. Yamaguchi, T. Komatsubara, A. Ozawa Osaka Elector-Communication University Y. Mizoi, T. Fukuda Japan Atomic Energy Agency Y. Wakabayashi, H. Makii Tohoku University N. Iwasa Kyushu University T. Teranishi Yamagata University S. Kato McMaster University (Canada) A.A. Chen Institute of Modern Physics (China) J. J. He

3. Contents 1.Physics motivation 2.Properties of the ( , p) reactions 3.Multiple – Sampling and Tracking Proportional Chamber 4. GEM – MSTPC for ( , p) reaction measurements Design GEM Gas gain study High rate heavy ion beam injection test 6. Schedule 7. Summary

4. Physics Motivation 11 C 12 C 13 C 13 N 14 N 15 N 12 N 16 O 17 O 18 O 9C9C 10 C 11 N 15 O 14 O 19 F 18 F 17 F 20 Ne 21 Ne 22 Ne 19 Ne 18 Ne stable unstable 22 Na 23 Na 21 Na 20 Na A: hot-CNO B: second hot-CNO C: 18 Ne( , p) 21 Na D: 18 Ne(2p,  ) 20 Mg E: 15 O(2p,  ) 17 F J. Phys. G: Nucl. Part. Phys. 25 (1999)R133 17 Ne Nove, SNe, X-ray burst Proton rich environment Novae, X – ray bursts early stage of supernova explosions ( p – process) 12 C(p, γ) 13 N(p, γ) 14 O(  ) 14 N(p,  ) 15 O(  ) 15 N(p,  ) 12 C hot CNO cycle second hot CNO cycle 18 Ne(α, p) 21 Na 14 O(α, p) 17 F (p, γ) 18 Ne(  ) 18 F(p, α) 15 O(  ) 15 O(p, α) 12 C The ( , p) reactions are important for break-out to the rp-process from the hot-CNO cycles, which converts the initial CNO elements into heavier elements.

5. Properties of ( , p) reactions T = 1 – 3 GK → Ecm = 1 – 3 MeV Estimated cross sections → less than 1 mb (in low energy region) 18 Ne( , p) 21 Na reaction cross sections (Calculated by a statistical model) Required conditions for experiments Low energy and high intensity RI beam E 10 5 pps High – efficient detector system higher than 15% He gas target RI beam is produced and separated by CRIB facility An active target detector system is useful detector!

6. X ∝ (Q R - Q L )/(Q R +Q L ) Y ∝ drift time Z ∝ Pad Number Multiple – Sampling and Tracking Proportional Chamber (MSTPC) Y. Mizoi, el al., NIMA 431(1999)122 T. Hashimoto, el al., NIMA 556(2005)339 8 Li( , n) 11 B reaction He gas + 8 Li beam He + CO 2 (10%) @ 120 torr Advantages and merits 1.The gas in the chamber serves as an active target. -> The solid angle is 4  and detection efficiency is about 100%. 2.The MSTPC can measure 3D trajectories and dE/dx along their trajectrories. -> It serves a sufficient target thickness without losing any information. The identification of the reaction is clearly performed. Y Z

7. The problem of MSTPC In the higher injection rate, output signals become unstable due to space charge gain limitation near the individual anode wire. A gating grid system was installed between the drift region and the proportional region. Rate dependence of the pulse height gated-grid off gated-grid on 0.5 kHz 2.6 kHz 3.6 kHz 0.3 to 5.6 kHz Trigger rate 20 cps 20% decrease Less than 2% 7% decrease at 113 kpps 42 kHz 113 kHz Insufficient suppression of drift electron by gating grid

8. gating – grid off gating – grid on noise  particles The problem of gating – grid We will use the TPC and Si detectors → This noise is serious problem … noise trigger

9. Gas – Electron Multiplier – MSTPC (GEM – MSTPC) Installing Gas Electron Multiplier (GEM) for much more high-rate beam injection up to 1MHz GEM – MSTPC e-e- e-e- GEM Wire MSTPC Other Merits of GEM – TPC Beam event? X position Pad number Energy loss Pad number Beam event? Reaction event! Event selection efficiency will be higher than old type MSTPC H.V. e- + + Cu Very high electric field inside holes High gas multiplication factor Quick absorption of positive ions

10. For ( , n) reactions Developing at KEK 1 st experiment : 8 Li( , n) 11 B For ( , p) reactions 1 st experiment : 18 Ne( , p) 21 Na Presentation of Ishiyama san Developing at CNS Two types of GEM – MSTPC

11. Z X Y High gain Low gain Two different gain region is need. Low gain region for heavy ion gas gain : 10 2 ～ 10 3 High gain region for proton gas gain : 10 5 GEM – MSTPC for the ( , p) reaction measurements 100 mm 275 mm 295 mm 100 mm 200 mm 33 mm 235 mm 4 mm Backgammon type pad GEM foil

12. Gas Electron Multiplier Two types of GEM Thin GEM; CERN standard type thickness: Kapton 50  m Cu 5  m x 2 hole: diameter 50  m - 70  m pitch 140  m 50  m 70  m 140  m 100mm Thick GEM; REPIC Insulator: FR – 4 Thickness (  m) Hole size (  m) Pitch (  m) Rim (  m) 400500700No 400300600No 20030060050 200 600No ThicknessHole size pitch rim

13. Gas gain study of GEM Test conditions Gas : He + CO 2 (10%) Pressure : 120 torr CERN standard GEM (double) ・ CERN standard GEM The gas gain is not enough → There is little number of gas molecules ・ Thick GEM The gas gain is more than 10 3 by low applied voltage → The gas gain attain 10 5 by by a multiple GEM configuration 200  m w/ rim 200  m w/o rim 400  m thick, 500  m hole 400  m thick, 300  m hole Required

14. High rate heavy ion beam injection test @ TRIAC (Details was reported by Ishiyama san) 400  m thick, 500  m hole TGEM Discharge phenomena appeared at around 10 4 pps 400  m thick, 300  m hole TGEM Discharge phenomena appeared less than 10 5 pps A small GEM hole size was adopted to obtain the same gas gain at low applied voltage anode GEM1 GEM2 Gas gain: 1.5 x 10 3 shield for Ion feed back anode GEM1 GEM2 Gas gain: 228 Gas gain: 32 The GEM – MSTPC can accept higher than 100 kpps without pulse height distortion!!

15. In 18 Ne case … The gas gain in low gain region is smaller than one of 8 Li case.  E( 18 Ne)/  E( 8 Li) = 5 (assuming same velocity) In 8 Li case, gas gain need to be 1.5 x 10 3 → gas gain need to be about 300 in 18 Ne case TGEMElectric field (V/cm/atm) 400  m thick, 300  m hole 58.4 200  m thick w/ rim 136.3 200  m thick w/o rim 84.3 How much need applied voltage? lowest The gas gain of this TGEM has time dependence Now, we are testing the 200  m GEM w/o rim

16. Schedule of development and physics run Physics run Measurement of the 18 Ne( , p) 21 Na reaction cross section Jan. Feb. Mar. Apr.May Offline test of 200  m thick TGEM w/o rim time dependence of gas gain etc… Offline test of GEM – MSTPC energy resolution, position resolution etc… Preparation of the DAQ system. Online test @ Pelletron (RIKEN) High rate a beam injection proton detection Online test @ Tandem acc. (University of Tsukuba) High rate heavy ion beam injection test Calibration run (Measurement of the 16 O( , p) 19 F reaction cross section)

17. Summary ・ We are developing the GEM – MSTPC for the astrophysical experiments. There are two types of GEM – MSTPC Type I : for (a, n) reaction measurements Type II : for (a, p) reaction measurements ・ The type II GEM – MSTPC has two gain region One is low gain region for Heavy Ion measurement The other one is high gain region for light particle measurement ・ The GEM – MSTPC can accept higher than 100 kpps beam by using multi GEM condition. → Low applied voltage condition of each GEM is necessary. → Multi GEM configuration is needed. ・ This test performed by using 400  m thick and 300  m hole GEM. The gas gain of this GEM has time dependence. → We are testing 200  m GEM w/o rim If it has no time dependence, we will adopt it.

19. Time dependence of gas gain

20. Position (mm) Field (relative value) 10 mm pitch No Si With Si Position (mm) 5 mm pitch Position (mm) 10 mm pitch Field Calculation with Si detector With Si No Si wire 20 mm10 mm Active area Field distortion is less than 1%

21. DAQ Non-stop digitizing and storing Candidate –COPPER II Framework (KEK) FADC 65MHz, 10bit –64ch Programmable digitizer (CAEN) FADC 65MHz, 14bit and time stamp module We are preparing COPPER II system COPPER board FADC FIFO Local bus CPU board CF memory Trigger module trigger Zero suppress etc.. DATA VME Detector Ethernet COPPER Network SW Event build Time stamp info.