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

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

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

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.

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.

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 !

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

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

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

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

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

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

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

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)

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

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…

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.

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