1. Development of the GEM – MSTPC for
(a, p) reactions of astrophysical interest
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
I will propose to measure the excitation function of 18Ne(a, p)20Na reaction for low energy region.

2. 2. Multiple – Sampling and Tracking Proportional Chamber (MSTPC)
Table of Contents
1.Introduction
Physics motivations of the proposed experiment
Properties of (a, p) reactions
2. Multiple – Sampling and Tracking
Proportional Chamber (MSTPC)
3. GEM – MSTPC
Gas Gain Study of GEM
Gas Gain Stability
High rate beam injection capability
4. Analysis and Preliminary results
5. Summary
It is outline of my presentation.
In this presentation, at first, I’ll talk about the physics motivation of this experiment.
Then, I’ll summarize the previous works.
Then, I’ll show you the goals of the experiments.
And then, I’ll explain the production of low-energy 18Ne beam at CRIB
Then, I’ll show you the experimental setup.
Then, I’ll explain the analysis and background rejection.
Then, I’ll show you the calculated result of yield estimation.
And then, I’ll show you the table of machine time request.
Finally, I’ll make a summary.

3. which converts the initial CNO elements into heavier elements.
Physics Motivation
20Na
21Na
22Na
22Na
23Na
stable
17Ne
18Ne
19Ne
20Ne
21Ne
22Ne
unstable
Nove, SNe, X-ray burst
A: hot-CNO
B: second hot-CNO
C: 18Ne(a, p)21Na
D: 18Ne(2p, g)20Mg
E: 15O(2p, g)17F
17F
18F
19F
14O
15O
16O
17O
18O
11N
12N
13N
14N
15N 9C
10C
11C
12C
13C
J. Phys. G: Nucl. Part. Phys. 25 (1999)R133
Proton rich environment
Novae, X – ray bursts, early stage of supernova explosions (np – process)
12C(p, γ)13N(p, γ)14O(b)14N(p, g)15O(b)15N(p, a)12C
hot CNO cycle
14O(a, p)17F (p, γ)18Ne(b)18F(p, a)15O(b)15O(p, a)12C
second hot CNO cycle
18Ne(a, p)21Na
The (a, 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.

4. (Calculated by a statistical model)
Properties of (a, p) reactions
T = 1 – 3 GK
→ Ecm = 1 – 3 MeV
Estimated cross section
→ less than 1 mb
(in low energy region)
(Calculated by a statistical model)
18Ne(a, p)21Na reaction
cross sections
The purpose of experiment is
measurement of the reaction cross section
with a statistical uncertainty better than 20%
Required conditions for experiments
Low energy and high intensity RI beam
E < 4 MeV/u and I > 105 pps
RI beam is produced and
separated by the CRIB facility
He gas target
High – efficient detector system
higher than 15%
An active target detector system is
a suitable detector!

5. Multiple – Sampling and Tracking Proportional Chamber (MSTPC)
Y. Mizoi, el al., NIMA 431(1999)122
T. Hashimoto, el al., NIMA 556(2005)339
dE ∝ total charge
x ∝ charge division
y ∝ drift time
z ∝ pad number
In the higher injection rate,
output signals become unstable
due to space charge limitation
near the individual anode wire.
Advantages and merits
1. The gas in the chamber serves as an active target.
-> The solid angle is 4p 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.
Installing Gas Electron Multiplier (GEM)
for much more high-rate beam injection up to 1MHz
GEM – MSTPC e- e-
H.V. e- + Cu
MSTPC
GEM
Wire
Very high electric field inside holes
(High gas multiplication factor)
Quick absorption of positive ions

6. GEM – MSTPC Multiple Sampling and Tracking Proportional Chamber with Gas Electron MultiplierY Z
295 mm
100 mm
Drift Region X
Beam
GEM
Readout Pattern
33 mm
100 mm
33 mm
275 mm
dE ∝ total charge
x ∝ charge division
y ∝ drift time
z ∝ pad number
33 mm
Backgammon type pad
4 mm
High gain
Requirements
Gas gain : low gain region 103
high gain region 105
Long time stability
High rate beam injection capability
Energy resolution : <10%
position resolution : < 2mm
235 mm
200 mm
Low gain

7. Gas Electron Multiplier
Two types of GEM
Thin GEM; CERN standard type
thickness: Kapton 50 mm
Cu 5mm x 2
hole: diameter 50 mm - 70 mm
pitch 140 mm
Thick GEM; REPIC
Insulator: FR – 4
Thickness (mm)
Hole size (mm)
Pitch
(mm)
Rim (mm)
400
500
700 No
300
600
200 50
50mm
70mm
140mm
100 mm
pitch
Thickness
Hole size
rim

8. Gas gain study of GEM Test conditions Gas : He + CO2 (10%)
Pressure : 120 torr
200 mm w/o rim
Required
・CERN standard GEM
The gas gain is low
→ small number of gas
molecules in a GEM hole.
400 mm thick, 500 mm hole
CERN standard GEM
(double)
400 mm thick, 300 mm hole
・Thick GEM
The gas gain is more than
103 under low applied
voltage condition.
→ The gas gain attain 105 by
a multiple GEM
configuration　
200 mm w/ rim
CERN standard GEM
(single)

9. The gas gain stability of 400 mm TGEM is no good
In our case, gas gain of 200 mm TGEM is satisfied
We adopted 200 mm TGEM

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

11. Position distortion (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 106 pps
The reason of this effect is ion feed back.
Efield = 1.5 kV/cm/atm
2.8 cm/msec
Injection rate (kpps)
Position distortion (mm)
200
2.2
400
3.6
The position distortion of drift direction can be corrected by the PPAC data
The GEM – MSTPC can be used to our experiment
with the satisfied performances

12. Preliminary Analysis and Preliminary results of 18Ne(a, p)21Na
Experimental setup
Particle identification
Preliminary
RF (arbitrary unit)
14O
17F
18Ne
11C
Beam intensity: 400 kpps in total
Purity: 81.6%
X position (arbitrary unit)

13. Preliminary p d a (Stopped in first layer) Si telescopes 3 4 1 MSTPC 2
Total energy (MeV) p d
a (Stopped in first layer)
Energy loss in first layer (MeV) 3 1 4
MSTPC 2 5

14. Preliminary GEM – MSTPC Raw signals L R Pulse height Raw data
(AL1, TL1)
(AL2, TL2)
Peak search
(AR1, TR1)
Coincidence check
TL1 = TR1 → accept
TL2 has no coincidence event → reject
Time
dE ∝ AL1 +AR1
x ∝ (AR1-AL1)/(AR1+AL1)
y ∝ drift time
z ∝ pad number
X position (arb. Unit)
Preliminary
Energy loss (arb. Unit)
Pad No.
Y position (arb. Unit)
Unfortunately, some pads were dead.
Basically , the GEM -- MSTPC worked well.
Pad No.
Pad No.

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

16. Summary
We developed the GEM – MSTPC for the measurement of (a, p) reactions of astrophysical interest.
Gas : He +CO2(10%) at a pressure of 160 torr
Gas gain was satisfied by using thick GEM
Long time stability of 200 mm GEM is good
Under the 400 kpps beam 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 measurement of 18Ne(a, p)21Na reaction have been performed.
The experiment have been finished successfully.
Reaction events are observed
The analysis is in progress.

18. the hot-CNO cycles, which converts the initial CNO elements into
Physics motivations
20Na
21Na
22Na
22Na
23Na
stable
17Ne
18Ne
19Ne
20Ne
21Ne
22Ne
unstable
A: hot-CNO
B: second hot-CNO
C: 18Ne(a, p)21Na
D: 18Ne(2p, g)20Mg
E: 15O(2p, g)17F
18F
X-ray bursts
17F
19F
14O
15O
16O
17O
18O
11N
12N
13N
14N
15N 9C
10C
11C
12C
13C
J. Phys. G: Nucl. Part. Phys. 25 (1999)R133
hot-CNO
12C(p, γ)13N(p, γ)14O(b)14N(p, g)15O(b)15N(p, a)12C
second hot CNO cycle
14O(α, p)17F(p, γ)18Ne(b)18F(p, α)15O(b)15O(p, α)12C
18Ne(α, p)21Na
Explosive hydrogen and helium burning is thought to be the main source of energy generation in novae, X-ray bursts, and also provides an important route for nucleosynthesis of elements up to masses 100 region via the rapid-proton capture process.
This figure shows the estimated temperature and density condition which allow break-out paths to the rp-process from the hot-CNO cycles. Region A characterizes typical condition hot-CNO cycles. Region B indicates the condition of the second hot-CNO cycle. The hot-CNO and the second hot-CNO cycles are linked by the 14O(a, p) reaction. Region C indicates the temperature and density region as which a sufficient reaction flow via 18Ne(a, p)21Na reaction lead to rp-process from the second hot-CNO cycles.
The typical densities in X-ray bursts and nova are estimated in this region.
Therefore, the 18Ne(a, p)21Na reaction is important for break-out to the rp-process from the hot-CNO cycle, which converts the initial CNO elements into heavier elements.
The lowest temperature in Regin C is about 0.6 GK.
In addition, according to some theories, this reaction has important role of the nucleosynthesis in Type II supernovae.
The typical expected temperature region in the type II supernove is 1 to 3 GK.
Therefore, we need the information of reaction cross sections at Ecm =0.5 and 3.8 MeV which corresponds T = GK.
The 18Ne(a, p)21Na reaction is important for break-out to the rp-process from
the hot-CNO cycles, which converts the initial CNO elements into
heavier elements.
We need the information of reaction cross sections at
Ecm = MeV which corresponds to T = GK.

19. Previous Works Direct method Indirect methods
Ex (MeV) Jπ
Gp (keV)
Ref
8.203(23)
(1+,2+,3+)b 34
[5], [6], [7], [8]
8.290(40) 53
[4], [8]
8.396(15)
[5], [6]
The absolute cross sections could not be determined
→The background rejection can not be performed clearly.
8.547(18)
(1-,2-,3-)b, 2+
40(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]
at T = GK
Gamow peak
region
Ref: PRC66(2002)05802
9.066(18)
[5]
(9.172(23))
[5],[7]
(9.248(20))
9.329(26)
Direct method
Direct measurement
(Ecm = MeV)
(Ecm = MeV)
Hauser-Feshbach
(9.387(22))
[7]
(9.452(21))
[5]
9.533(24)
[5], [7]
9.638(21)
3- a
9.712(21)
2+ a
Indirect methods
9.746(10)
[7]
9.827(44)
0+ a
[5], [7]
9.924(28)
(2, 3, 4)+
[5], [7], [9]
10.078(24)
[7]
10.190(29)
[5]
This figure shows the level scheme of the reaction.
This box indicates the Gamow peak regions from T9 =1 to 3.
In order to estimate the reaction rate of 18Ne(a, p)21Na, the resonant properties of excited states in 22Mg above the alpha threshold are needed.
The properties of those states were studied by indirect method.
Although some experimental efforts were made for the nuclear structure of 22Mg in this energy region, there is still only limited information.
Thus, it is very difficult to make a reasonable estimate of the 18Ne(a, p)21Na reaction rate.
In addition, two direct measurements have been performed at leuvan-la-nuvie.
The absolute cross sections could not be determined by these measurements. Because the experimental setup only scans a limited angular range.
However, some resonance state are observed. This figure shows the estimated reaction rate.
The solid line is the result form the direct measurements.
These experiment gives the estimated reaction rate.
However, if some resonances exist in the important energy region,
the absolute value would be changed.
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.
References
[2] 18Ne(a, p)21Na [4] 20Ne(3He, ng)
[5] 12C(16O, 6He) [6] 25Mg(3He, 6He)22Mg
[7] 24Mg(a, 6He) [8] 21Na(p, p)
[9] 22Al b+
10.297(25)
(2, 3, 4)+
[5], [7], [9]
10.429(26)
[5], [7]
10.570(25)
[2],[5],
10.660(28)
[5],[7]
In order to determine the reaction rate,
the absolute cross sections in the important energy region are needed.
10.768(17)
[2], [5], [7]
10.905(19)
[5], [7]
11.006(17)
[5],[7]
11.121(18)
(11.231)
[7]
11.313(20)
11.581(20)
(11.742)
11.881(20)
[7]

20. Low Energy 18Ne beam production at CRIB
The required conditions
Intensity : > 2 x 105 pps
Energy : <4 MeV/u (72 MeV)
Purity : higher than 70% F0
16O
16O
Experimental conditions
・E16O MeV/u
・I16O pnA
・3He gas target (Cryogenic target)
・3He(16O, 18Ne)n reaction
18Ne10+
18F9+
High pressure： high production rate & low transmission
Low pressure: low production rate & high transmission
For this purpose, the low-energy and high intensity 18Ne secondary beam and high efficient detector system are needed.
At first, I explain the low-energy 18Ne secondary beam production.
This table gives the required conditions of 18Ne beam.
The intensity of the beam is higher than 10^5 pps, the energy of the beam is 2.2 MeV/u, and the purity is about 90%.
In order to achieve these conditions, we will use these experimental conditions.
The 18Ne beam particles will be produced using the 3He(16O, 18Ne)n reaction.
We will select the 18Ne9+. In this situation, the primarily beam will be stopped in the D1 magnet.
The 18Ne9+, 18F9+, and some produced particles will pass through the D1 magnet.
The 18F9+ particles have almost same energy of 18Ne9+.
In order to reject the particle, we will use the very thin energy degrader.
If we use 0.7 mm Mylar foil, 18F9+ will stopped at the D2 magnet.
This figure shows the ions at F2 focal plane.
The most of impurities are swept out except for the 17F and 15O by using Wien Filter and the beam stopper in front of F3 focal plane.
The 17F and 15O particles can be rejected from 18Ne particles by TOF information.
This table gives the estimated condition of 18Ne beam.
There is the best gas pressure
Beam energy, intensity, and purity at F3 were measured
changing the production gas pressure.

21. Results Particle identification@F3 760 torr 560 torr 400 torr
Purity
70.3%
81.2%
15.3%
18Ne beam is contaminated by
11C beam
→　The velocities of 18Ne and
　　　　11C are almost same.
Intensity
3.3 x 104 pps
5.1 x 105 pps
Since beam emittance is worse, beam transmission is lower
Best condition
Cleared !
E = 3.7 MeV/u
DE = 0.8 MeV (s)

22. Experimental Setup Advantages and meritsy z
Beam monitor x
18Ne beam
He (90%) +CO2 (10%) mixed gas at
a pressure of 160 torr
・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 (DE)
・DE –E silicon telescope array (90 x 90 mm, 9 strips (single), t = 450 mm x 3 layer, 6 sets)
Energy losses in DE detector
Kinetic energies of light reaction products
Scattered angles of light reaction products
Advantages and merits
1. The gas in the chamber serves as an active target.
-> The solid angle is 4p 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.
Detection solid angle: ~ 15% of 4p
angular range:
0 < qcm < 140 degs. at Ecm = 1.5 MeV

23. The problem of gating – grid
trigger
noise
a particles
noise
gating – grid off
gating – grid on
We will use the TPC with Si detectors for proton measurement
→　This noise is serious problem …

24. Preliminary Measured dymanic range Ecm = 2.2 – 4.0 MeV
X position (arbitrary unit)
Preliminary
Total energy of 18Ne beam (MeV)
18Ne beam energy was measured by
a Si ditector as a function of a gas thickness
Measured dymanic range
Ecm = 2.2 – 4.0 MeV
He + CO2 (10%) , 160 torr
Gas thickness (mg/cm2)

25. Multiple – Sampling and Tracking Proportional Chamber (MSTPC)
Y. Mizoi, el al., NIMA 431(1999)122
T. Hashimoto, el al., NIMA 556(2005)339
He gas + 8Li beam
He + CO2 120 torr
8Li(a, n)11B reaction Y Z
X ∝　(QR- QL)/(QR +QL)
Y ∝ drift time
Z ∝ Pad Number
Advantages and merits
1. The gas in the chamber serves as an active target.
-> The solid angle is 4p and detection efficiency is about 100%.
2. The MSTPC can measure 3D trajectories and dE/dx along their trajectories.
-> It serves a sufficient target thickness without losing any information.
The identification of the reaction is clearly performed.

26. Insufficient suppression of drift electrons by gating grid
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
0.3 to 5.6 kHz
Trigger rate 20 cps
0.5 kHz
42 kHz
2.6 kHz
113 kHz
3.6 kHz
gated-grid off
gated-grid on
20% decrease
Less than 2%
7% decrease at
113 kpps
Insufficient suppression of drift electrons by gating grid

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

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