Development of a large-area position-sensitive
detector for the Rare-RI Ring at Riken
Sarah Naimi (Riken)

29 Mar. 2021 TCHoU workshop

Sarah Naimi

RI Beam Factory at RIKEN
3 injectors + cascade of 4 cyclotrons⇒ several to 345 MeV/nucleon
A variety of primary beams
World highest-intensity RI beams

ECR

RILAC
CSM

RILAC2RIPS

AVF

SAMURAI
ZeroDegree

Rare RI Ring

RRC
SRC

fRC

SCRIT

GARIS &GARIS2SLOWRI
SHARAQKISSBigRIPS

IRC

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Sarah Naimi

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Sarah Naimi

Gravitational Waves discovery
Neutron star mergers!

The light was also observed
This is very exciting for our field!!!

LIGO observatory in USA

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Sarah Naimi

5The nuclear physics????

Neutron is converted to proton via beta decay. Number of protons defines the element.

29 Mar. 2021 TCHoU workshop

Sarah Naimi『How were heavy elements made ?』rapid neutron capture: r-process
612=UNenc
2a=8ndNuablaroS50
N=Feβsayr escut
decapront
N eu6

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Sarah Naimi

7The nuclear physics????

Neutron is converted to proton via beta decay. Number of protons defines the element.

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Nuclear binding energy

Sarah Naimi

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Specifications
Circumference
Betatron tune
Momentum acceptanceTransverse acceptance
RI beam energy
Revolution frequency

Sarah Naimi

60.35m1.21 / 0.84
±0.5%
20π / 10π mm mrad
200 MeV/u
2.82MHz92012 Construction started
2013 Completed
2014 Test of devices
2015 1st & 2nd commissioning
2016 3rd commissioning2017 4th commissioning
2018 1st physics run
2020 Kicker upgrade29 Mar. 2021 TCHoU workshop

Sarah Naimi

RI Beam Factory at RIKEN
3 injectors + cascade of 4 cyclotrons⇒ several to 345 MeV/nucleon
A variety of primary beams
World highest-intensity RI beams

ECR

RILAC
CSM

RILAC2RIPS

AVF

SAMURAI
ZeroDegree

Rare RI Ring

RRC
SRC

fRC

SCRIT

GARIS &GARIS2SLOWRI
SHARAQKISSBigRIPS

IRC

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29 Mar. 2021 TCHoU workshop

Sarah Naimi

Production of RI beam at RIBF

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29 Mar. 2021 TCHoU workshop

Sarah Naimi

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Sarah Naimi

In November 2018: 122Rh,123,124Pd, 125Ag isotopes were measured
125Pd, 126Ag isotopes are planned to be measured in 2021

South of 132Sn(N=82)

Hongfu Li
PhD student at Riken

X29 Mar. 2021 TCHoU workshop

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Sarah Naimi
XSouth of 132Sn(N=82)

Production yields measured (1460)

New isotopes (2007–2018)
238U in-flight fission (119)Near 78Ni(Z=28, N=50)

124Xe P.F. (10)78Kr P.F. (3)70Zn P.F. (8)29 Mar. 2021 TCHoU workshop

Sarah Naimi

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Position detector
is too thick, energy loss introduces
uncertainty in beta measurement!
Massmeasurement
principle

F3

F5 position detector (PPAC)(dispersive plane)
β1 meas.

T0, T1 meas.

S0
m0 is known mass
m1 is unknown mass

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Sarah Naimi

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Position detector is too thick, energy loss introduces uncertainty in beta measurement!

F3

F5 position detector (PPAC)(dispersive plane)
β1 meas.

T0, T1 meas.

S0

S. Suzuki, NIMA 965 (2020)! = 38ps, eff = 95%, dE/E<10-5

29 Mar. 2021 TCHoU workshop

Sarah Naimi

17Large area position-sensitive DL-E-MCP
Thin C-foil à low energy loss
Acceleration spacer

Mirror grids
Thin foilYXZSEs
BeamMirror spacer

G. Hudson-Chang
Master (Surrey Uni.)

Acceleration
grid
MCP plates(Not to scale)

Foil (Mylar:1um) << PPAC thickness (Mylar:10um)
DL-MCP: ∅120mm ~ PPAC (240x150mm)

Delay LineZ. Ge, PhD(IMP/Riken)

R. Crane
Master (Surrey Uni)

rons

29 Mar. 2021 TCHoU workshop

Sarah Naimi

128Te 129Te 130Te

BetaD82

ecayr-process
bottleneck

Rapid-neutron capture

Neutronnumber124Ag

125Ag

126Ag

127Ag

128Ag

129Ag

130Ag

123Pd

124Pd

125Pd

126Pd

127Pd

128Pd

129Pd

N=77 N=78

N=79 N=80 N=81

Measured in 2018
Planned to be measured in 2021
Can be measured with 10% efficiency

N=82 N=83

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Sarah Naimi

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Before 2018: Efficiency issue

Lower acceptance!

Experiment

Before R3

A*er R3

Emittance at Kicker magnets center29 Mar. 2021 TCHoU workshop

After

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Redesign the injection optics for Rare-RI Ring

Efficiency: x14 times
Total R3 eff. 2%F3S0

ILC1

ILC2

RMD-4ELC

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Transmission Efficiency [%]BeforeSarah Naimi

Goal (10%)
10Exp. New Optics
1Exp. Standard Optics
Simulation

0.1

Injection
into ring

14 times
increase!!

rons

29 Mar. 2021 TCHoU workshop

Sarah Naimi

128Te 129Te 130Te

BetaD

82

eca
yr-process
bottleneck

Rapid-neutron capture

Neutronnumber

124Ag

125Ag

126Ag

127Ag

128Ag

129Ag

130Ag

123Pd

124Pd

125Pd

126Pd

127Pd

128Pd

129Pd

N=77 N=78

N=79 N=80 N=81

Measured in 2018
Planned to be measured in 2021
Can be measured with 10% efficiency

N=82 N=8321

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Sarah Naimi

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Large area position-sensitive DL-E-MCP
New kicker magnets configurationa bc dKicker magnets

DL-E-MCP could be placed inside the kicker
magnet to monitor emittance or just after29 Mar. 2021 TCHoU workshop

HIMAC test experiments

200MeV/u

Sarah Naimi

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Sarah Naimi

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HIMAC test experiments

A copper mask is put in front of the foil to make sure PPACs and DL-E-MCP are aligned

29 Mar. 2021 TCHoU workshop

HIMAC test experiments

Sarah Naimi

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Sarah Naimi

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HIMAC test experiments
Acceleration spacer

Mirror grids
Thin foilYXZSEs
Beam

Mirror spacer

Good position resolution overall the large area:• Homogenous electric field• High acceleration voltage (less spread)

Acceleration
grid
MCP plates

Homogenous electric field• New wiring method (tighter wires and same tension)• Smaller pitch
High acceleration voltage• Changed acceleration and mirror spacers(Not to scale)

Delay Line

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Sarah Naimi

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HIMAC test experiments
Acceleration spacer

Mirror grids
Thin foilYXZSEs
Beam

Mirror spacer

Pitch: distance between neighboring wires
Acceleration
grid

MCP plates(Not to scale)

Delay Line

Higher acceleration voltage leads to lessspread and therefore better resolution.
Spacer thickness is important to prevent
discharge at higher voltage.

29 Mar. 2021 TCHoU workshop

28Sarah Naimi

Voltage optimization method
Acceleration spacer

Keep acceleration voltage fixedand varying mirror voltage

Mirror grids

Y

Thin foil

XZSEs
Beam

Mirror spacer

Acceleration
grid
MCP plates(Not to scale)

Delay Linexy29 Mar. 2021 TCHoU workshop

Sarah Naimi

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Comparing two optimization methods

Position resolution in Y improved for method 2 without compromising position resolution in x

29 Mar. 2021 TCHoU workshop

Test results

Resolution=Sigma ofMCP – Foil
Ideally<1mm

Sarah Naimi

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Sarah Naimi

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Planned improvement of position resolution

G. Hudson-Chang
Master (Riken/Surrey)

Compact

Test experiment planned July 2021 at HIMAC

29 Mar. 2021 TCHoU workshop

32128Te 129Te 130Te

Protons

Summary

Sarah Naimi• Goal: Measure mass of n-rich nuclei beyond N=82

for r-process study• Challenge: efficiency of the Rare-RI Ring should
be increased.
• Solution: Large area thin-foil position-sensitive
DL-E-MCP detector for in-ring diagnostics andreduction of mass uncertainty systematic.
• Progress: Position resolution less than 2mm
relative to conventional detectors. Ideally it shouldbe less than 1mm• Improvement: Design of compact detector toreduce the spread and apply higher voltage. Digital
DAQ for better signal processing (collab. Korea).

BetaD

82

eca
yr-process
bottleneck

Rapid-neutron capture

NeutronnumberNeutrons

124Ag

125Ag126Ag

127Ag

128Ag

123Pd

124Pd

125Pd

126Pd

127Pd

N=77 N=78

N=79 N=80 N=81

129Ag

130Ag

128Pd

129Pd

N=82 N=83

Measured in 2018
Planned to be measured in 2021
Can be measured with 10% efficiency
Acceleration spacer

Mirror grids
Thin foil

YX

ZSEs
Beam

Mirror spacer

Acceleration
grid
MCP plates(Not to scale)

Delay Line

29 Mar. 2021 TCHoU workshop

ありがとうございました
Thank you for your attention

Sarah Naimi

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