Direct measurement of the 18 Ne( , p) 21 Na reaction with a GEM – MSTPC Takashi Hashimoto CNS, University of Tokyo Collaborators CNS S. Kubono, H. Yamaguchi, S. Michimasa, S. Ota, S. Hayakawa, H. Tokieda, D. Kahl, D. N. Binh KEK H. Ishiyama, Y. Hirayama, N. Imai, Y. X. Watanabe, S. C. Jeong, H. Miyatake Univ. Tsukuba K. Yamaguchi, T. Komatsubara Osaka ECU Y. Mizoi, T. Fukuda Tohoku Univ. N. Iwasa, T. Yamada Kyushu Univ. T. Teranishi JAEA H. Makii, Y. Wakabayashi Yamagata Univ. S. Kato McMaster Univ. A. A. Chen Inst. Mod. Phys. J. J. He

Table of Contents 1.Introduction Physics motivations of the proposed experiment Previous works 2. Production of low-energy 18 Ne beam at CRIB 3. Experimental Setup 4. GEM – MSTPC Gas Gain Study of GEM Gas Gain Stability High rate beam injection capability 5. Analysis and Preliminary results 6. Summary

Physics motivations 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 hot-CNO 12 C(p, γ) 13 N(p, γ) 14 O(  ) 14 N(p,  ) 15 O(  ) 15 N(p,  ) 12 C second hot CNO cycle 14 O(α, p) 17 F(p, γ) 18 Ne(  ) 18 F(p, α) 15 O(  ) 15 O(p, α) 12 C 18 Ne(α, p) 21 Na We need the information of reaction cross sections at E cm = MeV which corresponds to T = GK. 22 Na 23 Na 21 Na 20 Na The 18 Ne( , p) 21 Na reaction is important for break-out to the rp-process from the hot-CNO cycles, which converts the initial CNO elements into heavier elements. 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)R Ne X-ray bursts

Previous Works Gamow peak region at T = GK E x (MeV)JπJπ  p (keV) Ref 8.203(23)(1 +,2 +,3 + ) b 34[5], [6], [7], [8] 8.290(40)(1 +,2 +,3 + ) b 53[4], [8] 8.396(15)[5], [6] 8.547(18)(1 -,2 -,3 - ) b, (7)[4], [5], [7], [8] 8.613(20)3 - a, (2 + ) b 27(7)[5], [6], [7], [8] 8.754(15)4 + a [5], [6], [7] 8.925(19)3 - a [5], [7] 9.066(18)[5] (9.172(23))[5],[7] (9.248(20))[5] 9.329(26)[5] (9.387(22))[7] (9.452(21))[5] 9.533(24)[5], [7] 9.638(21)3 - a [5], [7] 9.712(21)2 + a [5] 9.746(10)[7] 9.827(44)0 + a [5], [7] 9.924(28)(2, 3, 4) + [5], [7], [9] (24)[7] (29)[5] (25)(2, 3, 4) + [5], [7], [9] (26)[5], [7] (25)[2],[5], (28)[5],[7] References [2] 18 Ne(a, p) 21 Na [4] 20 Ne( 3 He, ng) [5] 12 C( 16 O, 6 He) [6] 25 Mg( 3 He, 6 He) 22 Mg [7] 24 Mg(a, 6 He) [8] 21 Na(p, p) [9] 22 Al b+ Indirect methods (17)[2], [5], [7] (19)[5], [7] (17)[5],[7] (18)[5],[7] (11.231)[7] (20)[7] (20)[7] (11.742)[7] (20)[7] Ref: PRC66(2002)05802 Direct measurement (E cm = MeV) Direct measurement (E cm = MeV) Hauser-Feshbach Direct method The absolute cross sections could not be determined → The background rejection can not be performed clearly. In order to determine the reaction rate, the absolute cross sections in the important energy region are needed. If there are some resonances in the important energy region, the absolute value would be changed.

Experimental conditions ・ E 16O 6.8 MeV/u ・ I 16O 560 pnA ・ 3 He gas target (Cryogenic target) ・ 3 He( 16 O, 18 Ne)n reaction F0 16 O 18 F Ne 10+ The required conditions Intensity : > 2 x 10 5 pps Energy : <4 MeV/u (72 MeV) Purity : higher than 70% Low Energy 18 Ne beam production at CRIB High pressure ： high production rate & low transmission Low pressure: low production rate & high transmission There is the best gas pressure Beam energy, intensity, and purity at F3 were measured changing the production gas pressure.

Results Particle 760 torr560 torr 400 torr Purity 70.3% 81.2%15.3% 18 Ne beam is contaminated by 11 C beam → The velocities of 18 Ne and 11 C are almost same. Intensity 3.3 x 10 4 pps 5.1 x 10 5 pps Best condition Since beam emittance is worse, beam transmission is lower E = 3.7 MeV/u  E = 0.8 MeV (  ) C l e a r e d !

Experimental Setup He (90%) +CO 2 (10%) mixed gas at a pressure of 160 torr z x y ・ Beam monitor (2 PPACs ) Beam TOF (RF – PPAC) Beam position (x, y) ・ GEM-MSTPC (Active target) Multiple-Sampling and Tracking Proportional Chamber with Gas Electron Multiplier Three dimensional trajectories of beam particles and reaction products (x, y, z) Energy losses of them in the detector gas along their trajectories (  E) ・  E –E silicon telescope array (90 x 90 mm, 9 strips (single), t = 450  m x 3 layer, 6 sets) Energy losses in  E detector Kinetic energies of light reaction products Scattered angles of light reaction products Detection solid angle: ~ 15% of 4  angular range: 0 <  cm < 140 degs. at E cm = 1.5 MeV 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. 18 Ne beam Beam monitor

Z X Y High gain Low gain Requirements Gas gain : low gain region 10 3 high gain region 10 5 Long time stability High rate beam injection capability Energy resolution : <10% position resolution : < 2mm 100 mm 200 mm 33 mm 235 mm 4 mm Backgammon type pad GEM foil Drift Region Gas Electron Multiplier (GEM) Beam Readout Pattern GEM – MSTPC Multiple Sampling and Tracking Proportional Chamber with Gas Electron Multiplier dE ∝ total charge x ∝ charge division y ∝ drift time z ∝ pad number

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 low → little number of gas molecules in a GEM hole. ・ Thick GEM The gas gain is more than 10 3 under low applied voltage condition. → The gas gain attain 10 5 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

Gas gain stability The gas gain stability of 400  m TGEM is no good In 18 Ne case, gas gain of 200  m TGEM is satisfied We adopted 200  m TGEM

High beam injection rate capability Measurement of the injection beam rate dependence of the detector response beam ： 11 B, 6 MeV, 500 pps – 420 kpps 、 diameter: 1mm φ The energy and position resolution do not depend on beam injection rate. These results satisfy our requests Energy resolution : 8% position resolution : 1.7 mm

Beam injection rate dependence of drift velocity Drift time becomes longer with beam injection rate. The field distortion from ionized gas : 1.1 % at 10 6 pps The reason of this effect is ion feed back. Injection rate (kpps) Position distortion (mm) The GEM – MSTPC can be used to our experiment with the satisfied performances The position distortion of drift direction can be corrected by the PPAC data 2.8 cm/  sec E field = 1.5 kV/cm/atm

Analysis and Preliminary results Beam intensity: 400 kpps in total Purity: 81.6% 18 Ne X position (arbitrary unit) RF (arbitrary unit) 11 C 17 F 14 O Preliminary Particle identification Beam production conditions ・ E 16O 6.8 MeV/u ・ I 16O 560 pnA ・ 3 He gas target (Cryogenic target) ・ 3 He( 16 O, 18 Ne)n reaction ・ gas pressure of 3 He: 560 torr Preliminary Total energy of 18 Ne beam (MeV) Gas thickness (mg/cm 2 ) 18 Ne beam energy was measured by a Si derector as a function of a gas thickness Measured dymanic range E cm = 2.2 – 4.0 MeV He + CO 2 (10%), 160 torr

MSTPC Preliminary Si telescopes Energy loss in first layer (MeV) Total energy (MeV) p d   Stopped in first layer)

GEM – MSTPC Raw signals Pulse height Time Peak search (A L 1, T L 1) (A L 2, T L 2) (A R 1, T R 1) LR Coincidence check T L 1 = T R 1 → accept T L 2 has no coincidence event → reject Energy loss (arb. Unit) Pad No. X position (arb. Unit) Y position (arb. Unit) Unfortunately, some pads were dead. Basically, the GEM -- MSTPC worked well. Preliminary Raw data dE ∝ A L 1 +A R 1 x ∝ (A R 1-A L 1)/(A R 1+A L 1) y ∝ drift time z ∝ pad number

Typical reaction EventPreliminary 18 Ne 21 Na (?) 18 Ne 21 Na (?) 18 Ne Energy loss (arb. Unit) Pad No. X position (arb. Unit) Y position (arb. Unit) Reaction events are observed ! Analysis is in progress…

Summary Direct measurement of 18 Ne( , p) 21 Na reaction with the GEM – MSTPC have been performed at CRIB. Low energy 18 Ne beam beam energy : 3.7 MeV/u Energy Spread: 0.8 MeV Intensity: 400 kpps Purity: 81.6% GEM – MSTPC Gas : He +CO 2 (10%) at a pressure of 160 torr Gas gain was satisfied by using thick GEM Long time stability of 200  m GEM is good Under the 400 kpps injection Energy resolution: 8% Position resolutions: x direction : 1.7 mm y direction : 3.6 mm (distortion) → it can be collected by the PPAC information The experiment have been finished successfully. Reaction events are observed The analysis is in progress.

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 100  m Thick GEM; REPIC Insulator: FR – 4 Thickness (  m) Hole size (  m) Pitch (  m) Rim (  m) No No No ThicknessHole size pitch rim