The CRIB Project and the active target MSTPC

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Nov 14, 2013 (3 years and 8 months ago)

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The CRIB Project
and the active target
MSTPC

Takashi Hashimoto (from CRIB Collaboration)

Research Center for Nuclear Physics,

Osaka University

CRIB supporting members in CNS, Univ. of Tokyo:

Hidetoshi Yamaguchi (Lecturer),


Daid

Kahl

(
Postdoc
.)

Taro
Nakao

(
Postdoc
.)

with an Aid of Technical Staff:

N. Yamazaki, H.
Ninomiya
, K. Yoshimura


and RIKEN

S.
Kubono


in Collaboration with:

RIKEN, KEK, Kyushu, Tsukuba, Tohoku, Osaka, … (Japan)

McMaster

(Canada), CIAE, IMP (China), Chung
-
Ang
,
Ehwa
, SNU
(Korea), INFN
Padova
/Catania (Italy), IOP(Vietnam) and others.

Table of Contents

1. Low Energy RI beams

2. CRIB





Cryogenic Gas target






Wien Filter

3. Research Project





7
Li/
7
Be +
a

resonant elastic scattering





Direct measurement of
18
Ne(
a
, p)
21
Na reaction





using a active target detector system

4. Summary


Stellar astrophysical reactions :

T ~ 10
6
-
10
9

K (typically
keV

to a few
MeV
).



Low
energy is
s
uitable for nuclear
astrophysics and structure study.


Nucleosynthesis

proceeds
through
unstable nuclei
in some
processes(pp chain, CNO cycle,
r
-
,
rp
-
, processes etc.)


The Sun

SN1987A

Low Energy RI beam

In order to study nuclear astrophysics,

w
e require “Low Energy RI beam”

CRIB




C
NS
R
adio
-
I
sotope
B
eam separator

, operated by
CNS

(Univ. of Tokyo),
located at
RIBF

(RIKEN
Nishina

Center).



Low
-
energy(<10MeV/u) RI beams
by in
-
flight method.


Primary beam from K=70 AVF cyclotron.



Momentum (Magnetic rigidity) separation by “double achromatic” system, and
velocity separation by a Wien filter.



Orbit radius: 90 cm, solid angle: 5.6
msr
, momentum resolution: 1/850.





Intense secondary beam production using
cryogenic gas target

7
Be
4+

beam production via
7
Li(p, n)
7
Be

Primary

beam:
7
Li
2+
, 1.3
p
m
A

Production target: H
2


Pressure
: 730
torr

Temperature: 85 K


Secondary beam conditions

Energy:
4.0 MeV/u

P
urity
:
75%

(without degrader/ WF)

Intensity:
2 x 10
8

pps



H. Yamaguchi et al., NIMA (2008)

80 mm

f

20 mm

Wien Filter


1.5 m
-
long
HV electrodes
, 8 cm distant from each other,
±
200 kV applicable (stable up to
±

120kV), horizontal E field.



Dipole magnet
, max. 0.3 T vertical magnetic field.



Spending much effort for the
stabilization against discharge.

Low


Energy RI beam productions at
CRIB

Direct reactions such
as


(
p,n
)
,
(
d,p
)

and

(
3
He,n)

in
inverse kinematics are mainly
used for the production….
large
cross section


Many
RI beams
have been
produced at CRIB:

Typical intensity:
10
4
-
10
6

pps

RI beam at CRIB
/

Stable nuclei

Research Project (2010
-
)

Proton/alpha resonant scattering


26
Si+p
(Collaborated with Chung
-
Ang
, Korea)
H.S. Jung et al., published at PRC (2012).


7
Li/
7
Be+
a

(CNS)
H. Yamaguchi et al., PRC (2011).


21
Na+p,
22
Na+p

[
18
Ne(
a
, p
), Ne
-
Na cycle]
(IMP/CIAE, China)


17
F+p [Resonances for
14
O(
a
, p
)]
(IMP/CIAE, China)

Latest measurement in June!


Direct (
a
, p
) reaction
measurement using active
target
system (GEM
-
MSTPC
)


18
Ne(
a
, p
)

(CNS, Hashimoto (now at RCNP))


30
S(
a
, p
)

(CNS,
Daid

Kahl
)


22
Mg(
a
, p
)
(IOP, Vietnam , Nguyen Ngoc
Duy
)


44
Ti(
a
, p
)

(KEK,
Ishiyama
)

44
Ti beam test in May successful.


(
a
,
g
)

16
N

16
O*

12
C+a for
12
C(
a, g
)
(S. Cherubini, Catania, Italy)

Reaction mechanism


8
B+Pb

(
Padova
, Italy, C.
Signorini
)

β
-
decay


7
Be lifetime in metal

(Tohoku
Univ
,
Otsuki
)


7
Li(
a
,
g
)
11
B

…important as a production
reaction of
11
B
at
high
-
T

(
the
n
-
process in core
-
collapse supernovae
).


7
Be(
a
,
g
)
11
C

… one of the key reactions for
brake out
from

hot
p
-
p

chain to hot CNO cycle
,
relevant at high
-
T.



a
-
cluster structure in

11
B/
11
C

:


2
a
+
t

/ 2
a
+
3
He cluster states are known to
exist
(similar to the
dilute cluster structure
in
12
C.
)


Several “bands” which have
a
-
cluster
structure could be formed.



We can study the band and cluster
structure more in detail.

7
Li +
a
/
7
Be +
a

獴畤礠



“Thick target with inverse
kinematics”



Resonant elastic scatterings
can be measured at
q
cm
=180
deg.



11
C+p
; T.
Teranishi

et al., Phys.
Lett
. B (2003).


13
N+p
; T.
Teranishi

et al., Phys.
Lett
. B (2007).


21
Na+p
,
22
Mg+p
; J.J. He et al,
Eur

Phys. J (2008)
and Phys. Rev. C (2007).


7
Be+p
;

H. Yamaguchi et al., Phys.
Lett
. B (2009).




MCP

7
Li /
7
Be +
a

㬠䵥瑨潤


We applied the method for proton +RI beams,


but
how good it can work for
a
?


(
Especially for light nuclei, where Z is not much different from 2.)



Strong
a

resonances were successfully observed, and we determined
the
a

widths (
G
a
).
H. Yamaguchi et al., Phys Rev. C (2011).

T=3/2?
1/2?

Is
J
p

really
9/2
-
?

New!

7
Li +
a

㭒敳畬琠

7
Li +
a

㭒敳畬琠


Resonant reaction rates for the observed
resonances are compared with NACRE
evaluation




(including resonances below 11 MeV).











Conclusion:

No need to modify NACRE evaluation (for T
9
<5).


Newly proposed a negative parity band.


It may not be a simple rotational band,
but corresponds to 2
a
-
2n structure in
10
Be [Calc. by
Suhara

&
En’yo
]

7
Be +
a

㭒;獵s琠

11
C

12
C

13
C

13
N

14
N

15
N

12
N

16
O

17
O

18
O

9
C

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(
b
)
14
N(p,
g
)
15
O(
b
)
15
N(p,
a
)
12
C

second hot CNO cycle

14
O(α, p)
17
F(p, γ)
18
Ne(
b
)
18
F(p, α)
15
O(
b
)
15
O(p, α)
12
C

18
Ne(α, p)
21
Na

We need the information of reaction cross sections at

E
cm

= 0.5
-

3.8 MeV which corresponds to T = 0.6
-

3 GK.

22
Na

22
Na

23
Na

21
Na

20
Na

The
18
Ne(
a
, 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(
a
, p)
21
Na

D:
18
Ne(2p,
g
)
20
Mg

E:
15
O(2p,
g
)
17
F

J. Phys. G: Nucl. Part. Phys. 25 (1999)R133

17
Ne

X
-
ray bursts

18
Ne(
a
Ⱐ瀩
21
Na reaction

18
Ne(
a,
p
)
21
Na; Experimental setup

He (90%) +CO
2

(10%) mixed gas

at a
pressure of 160
torr

z

x

y

Advantages and merits

1. The gas in the chamber serves as an active target.


-
> The solid angle is 4
p

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.

GEM


MSTPC

Multiple


Sampling and Tracking proportional Chamber with GEM

dE



Q
L

+Q
R

X


Q
L


Q
R

Y


drift time

Z


Pad Number

GEM

SSD array

Readout Pattern

Performance of GEM


MSTPC I

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
%

(request: <10%)

position
resolution : 1.7
mm

(request: <2 mm)

Performance of GEM


MSTPC II

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)

200

2.2

400

3.6

The GEM


MSTPC can be used to our experiment

with the satisfied performances

2.8 cm/
m
sec

E
field

= 1.5 kV/cm/atm

Unfortunately, signals from some of pads were missed.

Basically , the GEM


MSTPC worked well.

Bragg curve and Tracks of


secondary beam

Low energy
18
Ne beam


beam energy : 3.7 MeV/u


Energy Spread: 0.8 MeV


Intensity: 400
kpps


Purity: 81.6%



(Impurity is mainly
11
C)

Pad No.

Pad No.

Pad No.

dE
/Pad (MeV)

X position (cm)

Y

position (cm)

18
Ne

11
C

Energy resolution:
7%

for
18
Ne


10%

for
11
C

X position resolution:
2 mm


for
18
Ne


3mm



for
11
C

Y position resolution:
0.1 mm

Typical event of
18
Ne(
a
Ⱐ瀩
21
Na reaction

Si telescopes

Total energy (MeV)

p

Energy loss in first layer (MeV)

Reaction events are observed !

Pad No.

Pad No.

Pad No.

dE
/Pad (MeV)

X position (cm)

Y

position (cm)

Analysis is in progress …

18
Ne

21
Na

18
Ne

21
Na

18
Ne

18
Ne

18
Ne

21
Na

18
Ne

Summary

CRIB

is a low
-
energy RI beam facility operated by CNS, University of Tokyo,
providing RI beams of good intensity and purity.

Manpower…
Not sufficient. We are making experiments in collaboration with
external groups.

Standard experiments:
Proton/alpha resonant scattering, direct (
a
,p
) reaction
measurement using an active target (GEM
-
MSTPC)


GEM
-
MSTPC

Basic performances are sufficient for

(
a
, p) reaction measurements

It has been used in several (
a
,p
) measurements.






18
Ne(
a
, p)
21
Na,
30
S(
a
, p)
33
Cl,
22
Mg(
a
, p)
25
Al

Developments are on going, to make it a more reliable and stable system.

(avoiding discharges, gating grid, trigger system, DAQ, analysis framework)

Resonant elastic scattering

7
Li+
a
,
7
Be+
a
…strong resonances were observed. The “thick target method with
inverse kinematics” could be applied to many nuclides. We can study
astrophysical reactions and
a
-
cluster structures.

GEM
-
MSTPC



Systematic measurement of excitation function of (
a
, p) reactions


If
we have large solid angle neutron detector,



we
can
measure
(
a
, n)/(
p,n
) type reactions


to study the r


process
nucleosynthesis





Decay spectroscopy


b



delayed
a

decay of
16
N
(related to
12
C +
a

reaction
)


Nucleon
transfer and/or fusion reaction with low


energy RI
beam





Nuclear astrophysics, Nuclear structure, Reaction mechanisms

Future progress

CRIB



Increase intensities of Low Energy RI beams


Primary beam intensity increase about 10
p
m
A

in near future.


The maximum intensity of secondary beam is estimated to 10
9

pps

!


RI beam intensity is limited by target window durability.





We are planning a window less gas target.

We welcome new users, ideas and collaboration!

contact: yamag@cns.s.u
-
tokyo.ac.jp

Future development plan

18
Ne(
a,
p
)
21
Na

11
C

12
C

13
C

13
N

14
N

15
N

12
N

16
O

17
O

18
O

9
C

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(
b
)
14
N(p,
g
)
15
O(
b
)
15
N(p,
a
)
12
C

second hot CNO cycle

14
O(α, p)
17
F(p, γ)
18
Ne(
b
)
18
F(p, α)
15
O(
b
)
15
O(p, α)
12
C

18
Ne(α, p)
21
Na

22
Na

22
Na

23
Na

21
Na

20
Na

The
18
Ne(
a
, p)
21
Na reaction is important for break
-
out to the
rp
-
process from

the hot
-
CNO
cycles.

A: hot
-
CNO

B: second hot
-
CNO

C:
18
Ne(
a
, p)
21
Na

D:
18
Ne(2p,
g
)
20
Mg

E:
15
O(2p,
g
)
17
F

J. Phys. G: Nucl. Part. Phys. 25 (1999)R133

17
Ne

X
-
ray bursts

Relevant energy (temperature):

E
cm

= 0.5
-

3.8 MeV (T = 0.6
-

3 GK).

CRIB status and related topics, 2011
-
2012


Due to the earthquake and a trouble at the AVF cyclotron, we
had no beam time during Mar. to Sep., 2011.


Jun. 2011,
”Review Meeting on CRIB Activities”.


Nov. 2011,
OMEG11 (Origin of Matter and Evolution of
Galaxies), hosted by CNS.


Mar. 2012,
Prof.
Kubono

retired.


Developments:


Ion source

Development of new beams (such as
42
Ca).


Accelerator/Beam line

“Core monitor” for non
-
destructive
readout of the beam current (
S. Watanabe et al., NIM A,
2011
)


Cryogenic target
Used in every experiment. (
H.Yamaguchi

et
al., NIM A, 2008.
)


Wien filter

Improvement of insulators, monitoring system.


Active target (GEM
-
MSTPC)


Used in
18
Ne(
a
, p),
30
S(
a
, p),
22
Mg(
a
,p
).


International collaborations at CRIB


CRIB experiments performed in 2007
-
2011,


by collaborated members of CNS and other institutes:

CRIB in RIBF


AVF alone, operation cost ~1/10 of
BigRIPS
.


Ion source / AVF/ CRIB…development under CNS
-
RIKEN collaboration (joint venture).


AVF

Gas Electron Multiplier

Two types of GEM

Thin GEM; CERN standard type

thickness: Kapton 50
m
m


Cu 5
m
m x 2

hole: diameter 50
m
m
-

70
m
m


pitch 140
m
m

50
m
m

50
m
m

70
m
m

140
m
m

100
m
m

1〰
m
m

Thick GEM; REPIC

Insulator: FR


4

Thickness
(
m
m)

Hole size
(
m
m)

Pitch

(
m
m)

Rim
(
m
m)

400

500

700

No

400

300

600

No

200

300

600

50

200

200

600

No

Thickness

Hole size

pitch

rim

Gas gain study of GEM

Test conditions

Gas : He + CO
2

(10%)

Pressure : 120 torr


CERN standard GEM


(50
m
m thick)


The gas gain is low




little number of gas


molecules in a GEM hole.


Thick GEM


(200
m
m or 400
m
m thick)


The gas gain is more than


10
3
under low applied


voltage condition.




The gas gain attain 10
5
by


a multiple GEM


configuration


Required

Signal and DAQ

Preamp:
rpa

211 (REPIC)

Conversion gain


0.8V/pc

Integration time


80 nsec


20 mV

400 nsec

DAQ:
COPPER II

FINESSE FADC card

50 MHz, 12 bit FADC

Raw signals

Pulse height

Time

P.
Nemethy

et al., NIM212(1983)273, T.
Hashimoto et al., NIMA556(2006)339

The pulse height defect was

less than 2%

The gating grid allows

the primary electrons to go through

only when the proper trigger is generated

and limits the multiplication.

Gating Grid System

Problem