1. Direct measurement of the 18Ne(a, p)21Na reaction
Takashi Hashimoto
Research Center for Nuclear Study (RCNP)
Osaka University
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. Production of low-energy 18Ne beam at CRIB 3. Experimental Setup
Table of Contents
1.Introduction
Physics motivations of the experiment
Previous works
2. Production of low-energy 18Ne beam at CRIB
3. Experimental Setup
4. GEM – MSTPC
Gas Gain Study of GEM
Gas Gain Stability
High rate beam injection capability
5. Preliminary results
6. Summary and possible expantion at CRIB
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. 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.

4. Previous Works Indirect methods References
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]
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
9.066(18)
[5]
(9.172(23))
[5],[7]
(9.248(20))
9.329(26)
(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
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]
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]

5. In order to determine the absolute reaction rate,
Measured excitation functions
The absolute cross sections could not be determined
→The clear background rejection might not be performed.
x 10 – x 100 ??
(Inverse reaction)
ANL annual report 2004
In order to determine the absolute reaction rate,
the absolute reaction cross sections including all possible transitions in the important energy region are needed.

6. Low Energy 18Ne beam production at CRIB (10days in 2010)
The required 18Ne beam 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 production target pressure： high production rate & low transmission
Low production target 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
as a function of the production gas pressure.

7. 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)

8. 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

9. GEM – MSTPC Multiple Sampling and Tracking Proportional Chamber with Gas Electron MultiplierY
GEM foil Z
Drift Region X
Beam
Gas Electron Multiplier
(GEM)
Readout Pattern
dE ∝ total charge
x ∝ charge division
y ∝ drift time
z ∝ pad number
33 mm
100 mm
33 mm
Backgammon type pad
33 mm
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

10. Gas gain study of GEM Test conditions Gas : He + CO2 (10%)
Pressure : 120 torr
200 mm w/o rim
・CERN standard GEM
(50mm thick)
The gas gain is low
→ little number of gas
molecules in a GEM hole.
Required
400 mm thick, 500 mm hole
CERN standard GEM
(double)
400 mm thick, 300 mm hole
・Thick GEM
(200 mm or 400 mm thick)
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

11. the gas gain stability of 400 mm TGEM is no good
In 18Ne case, gas gain of 200 mm TGEM is satisfied
We adopted 200 mm TGEM

12. 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 satisfy our requests

13. 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

14. Preliminary Preliminary results Preliminary Particle identification
Beam production conditions
・E16O MeV/u
・I16O pnA
・3He gas target (Cryogenic target)
・3He(16O, 18Ne)n reaction
・gas pressure of 3He: 560 torr
Preliminary
RF (arbitrary unit)
14O
17F
18Ne
11C
Beam intensity: 400 kpps in total
Purity: 81.6%
X position (arbitrary unit)
Preliminary
18Ne beam energy was measured by
a Si derector as a function of a gas thickness
Measured dymanic range
Ecm = 1.8 – 2.9 MeV
He + CO2 (10%) , 160 torr

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

16. Preliminary GEM – MSTPC Unfortunately, some pads were dead.
Energy loss (arb. Unit)
Pad No.
X position (arb. Unit)
Y position (arb. Unit)
Preliminary
GEM – MSTPC
Unfortunately, some pads were dead.
Basically , the GEM -- MSTPC worked well.

17. Preliminary Typical reaction Event Reaction events are 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 are observed !
We will finish the analysis in this year

18. Summary
Direct measurement of 18Ne(a, p)21Na reaction with the GEM – MSTPC
have been performed at CRIB.
　　Low energy 18Ne beam
beam energy : MeV/u
Energy Spread: MeV
Intensity: kpps
Purity: %
GEM – MSTPC
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 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
Analysis is in progress.
We will finish the analysis in this year.

19. Future plan and possible expansion at CRIB
・ Systematic measurement of excitation function of (a, p) reaction
30S(a, p)33Cr →　The experiment was Done. Analysis is progress.
22Mg(a, p)25Al →　will be performed in last half of this FY.
◎If we have large solid angle neutron detector,
we can meausre (a, n)/(p,n) type reactions
to study the r – process nucleosynthesis
・ Nuclear reaction with low energy RI beam to study nuclear structure
and/or reaction mechanisms
Resonant scattering of proton or a particle
→ Teranishi san and Yamaguchi san’s talk
(multi)nucleon transfer and/or fusion reaction
・ Decay spectroscopy
16N (related to 12C + a reaction) →　will be performed in last half of this FY.
(Spokesperson: S. Cherubini)
In beam decay spectroscopy
For example, search for the two – proton decay
(to study di – proton correlation and/or 2 proton capture reaction)
→ feasibility study is needed

21. 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
100mm
pitch
Thickness
Hole size
rim