Particle identification of RI beam

in Sn region with the SAMURAI spectrometer

RIKEN Nishina Center

Masaki Sasano

Many slides are taken from a presentation by J. Yasuda in

EMIS2015, May 15, 2015

Collaborators

M. Sasano, H. Baba, W. Chao, M. Dozono, N. Fukuda, N. Inabe, T. Isobe, D. Kamaeda,

T. Kubo, M. Kurata-Nishimura, E. Milman, T. Motobayashi, H. Otsu, V. Panin, W. Powell, M. Sako,

H. Sato, Y. Shimizu, H. Sakai, L. Stuhl, H. Suzuki, T. Suwat, H. Takeda, T. Uesaka, K. Yoneda,

J. Zenihiro,

T. Kobayashi, T. Sumikama, T. Tako,

T. Nakamura, Y. Kondo, Y. Togano, M. Shikata, J. Tsubota,

K. Yako, S. Shimoura, S. Ota, S. Kawase, Y. Kubota, M. Takaki, S. Michimasa, K. Kisamori,

C.S. Lee, H. Tokieda, M. Kobayashi, S. Koyama,

J. Yasuda, T. Wakasa, S. Sakaguchi,

T. Murakami, N. Nakatsuka, M. Kaneko,

Y. Matsuda,

D. Mucher, S. Reichert,

R.G.T. Zegers, E.D. Bazin, N. Kobayashi,

G. Jhang, J.W. Lee

A. Krasznahorkay

Outline

• Background of 132Sn(p,n) study

• Experimental setup for 132Sn(p,n) reaction at 250 MeV/u

• Particle identification (PID) analysis by SAMURAI

• How charge state appears in the PID plot

• Future prospects and ideas

Charge-Exchange (CE) reactions

β-decay

CE

A,Z A,Z±1

en

erg

y

Ca

nn

ot a

cce

ss b

y β

-de

ca

y (p,n), (3He,t), (n,p), (t,3He), …

n p

𝝈 𝒕±

𝝈 𝒕±

NN

Giant

resonance

T=1, S=1,L=0 induced by 𝝈 𝒕±strength : B(GT)

Charge exchange reactions

Need to handle RI beams with intermediate energies

from 100 to 300 MeV

Overview of (p,n) studies for RI beam

@NSCL, MSU

S80056Ni

12Be8He

@RIKEN RIBF

SHARAQ

K.Yako et al.,

H. Sakai et al.,

132Sn (the data of today’s talk)

double magic nuclei far from stabilityperformed @RIBF SAMURAI, April 2014

PRL121 (2018) 132501.

M.Sasano et al.,

11Li, 14Be, L. Stuhl et al. @ SAMURAI

Charge state population for Sn beams

0

0.1

0.2

0 500 1000 1500 2000 2500

rati

o

Kinetic energy [MeV]

Z-Q=1 state ratio

(p,n) measurement with WINDS + SAMURAI

• Beam

• High Intensity : >10^4 pps

• Intermediate kinetic energy : 200~300 MeV/u

• can access to far from the stability line

• Neutron detection

• WINDS(Wide angle Inverse kinematics Neutron

Detectors for SHARAQ) : 73 scintillators

• cover wide angular range

• Residue tag

• SAMURAI

• Large acceptance

• measure all decay particle in one setting

BigRIPS

WINDS

SAMURAI

132Sn beam production

• Beam energy after F7: 270 MeV/u

•Total beam Intensity

• 1.4 x 10^4 pps

•PID by BigRIPS

• σZ = 0.24

• σA/Q = 0.0014

•Purity

• 132Sn : 40%

purity [%]

132Sn 40.11

133Sn 9.47

131Sn 9.50

135Sb 3.88

134Sb 4.28

130in 3.24

129In 1.96Z A/Q

σZ = 0.24

4.1σ separation

σAOQ = 0.0014

5.0σ separation

A/Q

Z

PID plot

132Sn

134Sb

130In

135Sb

5σ separation

Experimental setup

SAMURAI

n

132Sn

270 MeV/nucleon

WINDS

Liq. H

60mm phi

11mmt

132Sb*

FDC2

drift chamber

ICF

ion chanber

HODS

plastic TED

crystal

decay-n

NEBULA

—> P

—> Z, beta

—> charge state

—> tag for

n-decay channel

T. Kobayashi et al., NIM B371, 294 (2013)

Nakamura’s & Otu’s talks on Monday

Damping of beam energies

0

50

100

150

200

250

300

(MeV)

Requirements on SAMURAI

• Large acceptance

• all decay channel with multi-nucleon emission can be

measured in one setting

• momentum spread ~2%

• Good PID resolution for heavy residue

• 5σ separation for A & Z in order to improve S/N

TOF analysis

• Plastic counter HODS & SBT1,2

• HODS : 6 plastic scintillation with size of 450 x 100 x 5 mm3

• SBT1,2 : 130 x 130 x 5 mm3

• FPL ~12.5 m

• Resolution estimation

• Empty cell & beam trigger

→ SBT1,2 timing resolution (average of SBT1,2)

→ σt = 17ps (w/ slew correction)

<—> σt = 46 ps (w/o slew correction)

→ TOF (SBT1,2-HODS) : σ = 63ps

TOF(SBT1,2—HODS)

@ Empty cel & Beam trigger

σ = 63ps

[ns]

SBT slew correction

SBT1 Qmean [ch]

TO

F (

SB

T1

-SB

T2)

[ns]

σ ~ 0.9 ns

—> σt ~ 0.5 ns

SAMURAI

SBT1,2

HODS

σ ~ 0.4 ns

—> σt ~ 0.2 ns

Momentum analysis

• Input parameter

• Upstream vector (X1, A1), Magnetic Field, Downstream

position (X2)

• A1 was derived by using 3 tracking detectors

High angular resolution σA ~0.3 mrad

<—> σA~0.8 mrad (just use 1 tracking chamber)

Resolution : P/σP = 1300

<—> P/σP = 800 (just use 1 tracking chamber for ini. p)

search Rigidity

B=2.56TX1,A1

X2

P/σP =1300

P/σP =800

∆Rigidity [MeV/c]

rigidity @BigRIPS

rig

idity @

SA

MU

RA

I

use 3 tracking detectors

FDC1

FDC2

BDC1,2

∆E analysis

• Energy loss at plastic scintillator HODS

• HODS thickness : ~ 6 mm

• Non-uniformity ~ 20%

• Energy loss ~ 6000 MeV

• Correct position dependence by using

FDC2 tracking information

➡ Resolution : σΔE/ΔE = 0.4%

HO

DS

lig

ht o

ut p

ut [c

h]

HOD y-postion [mm]

correct position dep.

Z=50

Z=49

Z=48Z=51

HODS light out put [ch]

4

5

6

7

0 125 250 375 500

4

5

6

7

0 125 250 375 500

4

5

6

7

0 125 250 375 500

4

5

6

7

0 125 250 375 500

4

5

6

7

0 125 250 375 5004

5

6

7

0 125 250 375 500

4

5

6

7

0 125 250 375 500

HODS thickness

Y position [mm]

Th

ickn

ess [m

m]

HODS#1 #2

#4#3

#5

#7

#6

—> Non-uniformity ~20%

HODS#5

Stability of dE counter (plastic scintillator)

•Gain attenuation

•especially for beam hit bar

•Normalization parameter for ∆E has been corrected for each RUN

PMT w/ booster will be help to solve this problem

RUN NUMBER

~20kHz HODS#4 HODS#5Beam hit bar Fragment hit bar

Lig

ht

outp

ut (c

h)

~2kHz

RUN NUMBER

~40h ~40h

Comparison between BigRIPS and SAMURAI

(unreacted events with empty cell)

132Sn

Sn isotope

Empty cell RUN

beam trigger

131Sn

134Sb

130In

A/Q

Z

132Sn

134Sb

130In

135Sb

5σ separation

σZ = 0.22 σA/Q =

0.0032σZ = 0.24 σA/Q =

0.0014

PID for (p,n) reaction residues

132Sn132Sb

131Sb+n

130Sb+2n

129Sb+3n

(p,n)6MeV

13.7MeV

19.3MeV

Z distribution

Tail component ~ 1%

→

Detector response

or effect of charge state equilibrium?

→ Not so significant for this case

132Sn

132Sn on Liq.H target

slice this region

tail

~1%

Charge states in PID

• charge changing after F7

• Z>Q : ~10% (calculation by GLOBAL code)

PID plot for Sb isotope

131Sb51+ 132Sb51+

130Sb50+

charge state

A/Q

Z

Charge state separation

• Charge state

• 129Sb50+ : A/Q = 2.58

• 130Sb50+ : A/Q = 2.6

• AOQ(132Sb51+)-AOQ(129Sb50+)/σAQO ~ 2σ

• Coincidence with TED (id=21)

•Select lower total energy region

• A/Q =2.58,2.6 region are enhanced

‣ TED information is useful to separate Charge

state

129Sb50+?

130Sb 131Sb 132Sb

Z

A/Q

TE

D p

uls

e h

ight (c

h)

A/Q

130Sb50+?

129Sb50+?130Sb50+?

PID plot for Sb isotope

Pattern of charge states in PID for Sn region

Z

A/Q

132Sb(51+)

130Sn(50+)

130Sb(50+)

50

51

51+dZ

Energy losses in HODS

132Sb(51+)

130Sn(50+)

130Sb(50+)

@ the same rigidity

(5.54081 Tm)

6 mm

→ ~50% energy loss

→ Close to Bragg peak

Rebel w/o a cause:

The Chicken Race

As a function of thickness

Z

A/Q

132Sb(51+)

130Sn(50+)

130Sb(50+)

50

51

51+dZ

-1.5

-1

-0.5

0

0.5

1

1.5

2

0 5 10 15

dZ

Thickness of HODS plastic scintillator

(mm)

Better setup is…

132Sb(51+)

130Sn(50+)

130Sb(50+)

@ the same rigidity

(5.54081 Tm)

-1.5

-1

-0.5

0

0.5

1

1.5

2

0 5 10 15

Thickness of HODS plastic scintillator

(mm)

Uniformity of thickness must be controlled

PID

gate 1PID

gate 2,3

Future plan…

@NSCL, MSU

S80056Ni M.Sasano et al.,

Z ~ 90 region

Difficulties in Z~90 region @ 250 MeV/u

• A/Q separation is more difficult

→ Improve position and time resolution of detectors

for rigidity and tof analysis

• Short stopping range :

12.2 mm (CH2) → 20.4 mm (CH2)

→ Minimize the material thicknesses

Smaller reaction loss

• Large dE/dX

→ uniformity of the material thicknesses is required

• Charge state is dominant :

Q = Z – 1 is the main component

broader energy loss distribution

→ Measure Bragg curve itself

• Fission also occurs

→ Energy losses for Z ~ 30 to 50 region must be covered

Higher granularity to detect two fragments

Range counter

238U(Q+)

…

132Sn

70Zn

Si / SiC detectors

• Uniformity of Si wafer : ~ several 0.1%

• Strip detectors : 100 um strip size

→ dX ~ 30 um in sigma

Higher position and angular resolutions

• Thin (~50 um) layers for timing measurements

• Signal amplifications with electronics

→ Multi gain preamplifier

• Si wafer size available in market : 300/450(?) phi

Weak point : radiation damage

→SiC: stronger radiation hardicity (wafer size : 150 phi)

Higher granularity

…

50 um 300 um x ~20

Possible setup

• Vertical parallel

• Horizontal focus transport

SiC tracker

Si tracker / range counter

x

y

Summary

• PID plot is made for reaction residues from the 132Sn(p,n) reaction at

250 MeV/u using the SAMURAI spectrometer

• ~10% goes to charge states (Q<Z).

• Position of the charge state moves as a function of the HODS plastic

scintillator → Range counter

• Ultimate (?) solution: Si/SiC TOF/tracker/range counters

Thank you very much!