direct measurement of the 18 ne( , p) 21 na reaction with a gem – mstpc takashi hashimoto cns,...
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Direct measurement of the 18Ne(, p)21Na reaction with
a GEM – MSTPCTakashi Hashimoto
CNS, University of Tokyo
CollaboratorsCNS S. Kubono, H. Yamaguchi, S. Michimasa, S. Ota, S. Hayakawa, H. Tokieda, D. Kahl, D. N. BinhKEK H. Ishiyama, Y. Hirayama, N. Imai, Y. X. Watanabe, S. C. Jeong, H. MiyatakeUniv. Tsukuba K. Yamaguchi, T. KomatsubaraOsaka ECU Y. Mizoi, T. FukudaTohoku Univ. N. Iwasa, T. YamadaKyushu Univ. T. TeranishiJAEA H. Makii, Y. WakabayashiYamagata Univ. S. Kato McMaster Univ. A. A. ChenInst. Mod. Phys. J. J. He
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Table of Contents
1.Introduction Physics motivations of the proposed experiment Previous works
2. Production of low-energy 18Ne beam at CRIB 3. Experimental Setup4. GEM – MSTPC Gas Gain Study of GEM Gas Gain Stability High rate beam injection capability
5. Analysis and Preliminary results6. Summary
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Physics motivations
11C 12C 13C
13N 14N 15N12N
16O 17O 18O
9C 10C
11N
15O14O
19F18F17F
20Ne21Ne22Ne19Ne18Nestable
unstable
hot-CNO 12C(p, γ)13N(p, γ)14O()14N(p, )15O()15N(p, )12C
second hot CNO cycle14O(α, p)17F(p, γ)18Ne()18F(p, α)15O()15O(p, α)12C
18Ne(α, p)21Na
We need the information of reaction cross sections at Ecm = 0.5 - 3.8 MeV which corresponds to T = 0.6 - 3 GK.
22Na22Na23Na21Na20Na
The 18Ne(, 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.
A: hot-CNOB: second hot-CNOC: 18Ne(, p)21NaD: 18Ne(2p, )20MgE: 15O(2p, )17F
J. Phys. G: Nucl. Part. Phys. 25 (1999)R133
17Ne
X-ray bursts
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Previous Works
Gam
ow
peak
reg
ion
at
T =
0.6
- 3
GK
Ex (MeV) Jπ 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, 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]
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]
10.078(24) [7]
10.190(29) [5]10.297(25) (2, 3, 4)+ [5], [7], [9]
10.429(26) [5], [7]
10.570(25) [2],[5],
10.660(28) [5],[7]
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+
Ind
irect
meth
od
s
10.768(17) [2], [5], [7]
10.905(19) [5], [7]
11.006(17) [5],[7]
11.121(18) [5],[7]
Ref: PRC66(2002)05802
Direct measurement (Ecm = 1.9 - 3.0 MeV) Direct measurement (Ecm = 2.5 - 3.0 MeV) Hauser-Feshbach
Dir
ect
meth
od
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.
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Experimental conditions・ E16O 6.8 MeV/u・ I16O 560 pnA・ 3He gas target (Cryogenic target)・ 3He(16O, 18Ne)n reaction
F0
16O16O
18F9+
18Ne10+
The required conditionsIntensity : > 2 x 105 ppsEnergy : <4 MeV/u (72 MeV)Purity : higher than 70%
Low Energy 18Ne beam production at CRIB
High pressure : high production rate & low transmission Low pressure: low production rate & high transmission
There is the best gas pressureBeam energy, intensity, and purity at F3 were measuredchanging the production gas pressure.
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ResultsParticle 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
Best conditionSince beam emittance is worse, beam transmission is lower
E = 3.7 MeV/uE = 0.8 MeV ()
Cleared !
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Experimental Setup
He (90%) +CO2 (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 Ecm = 1.5 MeV
Advantages and merits1. 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.
18Ne beam
Beam monitor
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Z
X
Y
High gain
Low 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
100 mm
200
mm
33 m
m
33 mm33 mm
235
mm
4 m
m Backgammon type pad
GEM foil
Dri
ft R
eg
ion
Gas Electron Multiplier(GEM)
Beam
Readout Pattern
GEM – MSTPC Multiple Sampling and Tracking Proportional Chamber with Gas Electron Multiplier
dE ∝ total chargex ∝ charge divisiony ∝ drift timez ∝ pad number
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Gas gain study of GEM
Test conditionsGas : He + CO2 (10%)Pressure : 120 torr
CERN standard GEM
CERN stan
dard G
EM
(dou
ble)
・ 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 103 under low applied voltage condition. → The gas gain attain 105 by a multiple GEM configuration
200
m w
/ ri
m200
m w
/o r
im
400
m t
hic
k,
500
m h
ole
400
m t
hic
k,
300
m h
ole
Req
uir
ed
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Gas gain stability
The gas gain stability of 400 m TGEM is no good
In 18Ne case, gas gain of 200 m TGEM is satisfied
We adopted 200 m TGEM
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High beam injection rate capability
Measurement of the injection beam rate dependence of the detector responsebeam : 11B, 6 MeV, 500 pps – 420 kpps 、 diameter: 1mmφ
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
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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.
Injection rate (kpps)
Position distortion (mm)
200 2.2
400 3.6
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
Efield = 1.5 kV/cm/atm
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Analysis and Preliminary results
Beam intensity: 400 kpps in totalPurity: 81.6%18Ne
X position (arbitrary unit)
RF
(arb
itra
ry u
nit
)
11C
17F
14O
PreliminaryPreliminaryParticle identification Beam production conditions
・ E16O 6.8 MeV/u・ I16O 560 pnA・ 3He gas target (Cryogenic target)・ 3He(16O, 18Ne)n reaction ・ gas pressure of 3He: 560 torr
PreliminaryPreliminary
Tota
l en
erg
y of
18N
e b
eam
(M
eV
)
Gas thickness (mg/cm2)
18Ne beam energy was measured by a Si derector as a function of a gas thickness
Measured dymanic range Ecm = 2.2 – 4.0 MeV
He + CO2 (10%) , 160 torr
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MSTPC
0
12
3
45
PreliminaryPreliminary
Si telescopes
Energy loss in first layer (MeV)
Tota
l en
erg
y (M
eV
)
p d
Stopped in first layer)
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GEM – MSTPC Raw signals
Pu
lse h
eig
ht
Time
Peak search(AL1, TL1)(AL2, TL2)
(AR1, TR1)
L R
Coincidence check TL1 = TR1 → acceptTL2 has no coincidence event → reject
En
erg
y lo
ss (
arb
. U
nit
)
Pad No.
Pad No.
Pad No.X
posi
tion
(arb
. U
nit
)Y
p
osi
tion
(arb
. U
nit
)
Unfortunately, some pads were dead.Basically , the GEM -- MSTPC worked well.
PreliminaryPreliminary
Raw data
dE ∝ AL1 +AR1x ∝ (AR1-AL1)/(AR1+AL1)y ∝ drift timez ∝ pad number
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Typical reaction Event
PreliminaryPreliminary
18Ne 21Na (?)
18Ne
21Na (?)
21Na (?)
18Ne
En
erg
y lo
ss (
arb
. U
nit
)
Pad No.
Pad No.
Pad No.X
posi
tion
(arb
. U
nit
)Y
p
osi
tion
(arb
. U
nit
)
Reaction events are observed !
Analysis is in progress…
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SummaryDirect measurement of 18Ne(, p)21Na reaction with the GEM – MSTPC have been performed at CRIB.
Low energy 18Ne beam beam energy : 3.7 MeV/u Energy Spread: 0.8 MeV Intensity: 400 kpps Purity: 81.6% 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 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 observedThe analysis is in progress.
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Gas Electron Multiplier
Two types of GEM
Thin GEM; CERN standard typethickness: Kapton 50 m Cu 5m x 2hole: diameter 50 m - 70 m pitch 140 m
50m50m70m
140m
100m
100m
Thick GEM; REPIC Insulator: FR – 4 Thickness
(m)Hole size
(m)Pitch
(m)
Rim (m)
400 500 700 No
400 300 600 No
200 300 600 50
200 200 600 No
Thickness Hole size
pitch
rim