Development of solid hydrogen target in RIKEN RIKEN T. Ohnishi, H. Takeda, T. Suda KEK S. Ishimoto,...

Development of solid hydrogen target in RIKEN

RIKEN T. Ohnishi, H. Takeda, T. SudaKEK S. Ishimoto, S. SuzukiRCNP Y. TakahashiANL I. Tanihata

IntroductionSystemSolid hydrogen target with thin filmWindowless solid hydrogen targetSummary

Solid hydrogen target for RI beam experiment

Introduction

High energy and angular resolutions are needed.High energy and angular resolutions are needed.

1. Thin and flat target2. Uniform density3. Low background

Windowless solid hydrogen targetSolid hydrogen target with thin film

Proton elastic scattering, (p, 2p) reactions and etc..

t=1～ 5 mm d=20～ 30 mm

Requirements

Previous workTRIUNF, KEK

Cooling system: Liquid He system

For RI beam

Small system: to cover large solid angle and set easily on the beam lineLarge target: d > 20 mm

KEK: t=5～ 10 mm, d=10～ 20 mm

We develop small system and more thinner target.

Window less solid hydrogen target

TRIUNF: P. E. Knowles,et. al. Nucl. Instr. Meth. A368(1996)604.KEK : S. Ishimoto, el. al. Nucl. Instr. Meth. A480(2002)314.

System Gas Flow system

Cryostat

Vacuum Chamber

Cryostat: SUMITOMO RDK-415D Cooling power 1.5W@4KGas Flow system: Pressure ControlPt-Co resistance thermometerRadiation shield: Copper cylinder

Cell

2nd stage

1st stage

Copper block

H2 tube368mm

Solid hydrogen target with thin film300K G-H2 in/out

t=3 mm

Stycast-2850FT

PtCo thermometer

Mylar φ30 mm

300K G-H2 in/out

Stycast-2850FT

Stycast-1266PtCo thermometer

11min 20sec

Pset=60 Torr

Result

Good result

3min 40sec

Pstart=0.35 atmSolidLiquid

Bad result

T=3.7K

T=3.7K

50 μm Mylar

Liquid

Solid

Void

Liquid

Keyence LK500

H.R. Mode; 350 +/- 100 mm

Linearity; +/- 0.1% of FS

Resolution; 10 µm

Measurement of thickness

Vacuum

x

L Target

LK500

LASER MEASUREMENT; 25 MICRON MYLAR SHT

L = -0.129369 x + 64.933339

55

56

57

58

59

60

61

62

63

64

65

42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65

LASER POSITION X (mm)

LENGTH L (mm)

1ST2NDFIT DATAEmpty

80 Torr60 Torrê¸å` (FIT DATA)ê¸å` (Empty)

d = 0.6 +/- 0.05 mm

t=3 + d = 3.6 mm

3 mmd

25 μm Mylar

Experiment

R378@RIKEN

Windowless solid hydrogen target

t=7

He gas5 atm

Result

After 10 days

H2 FlowStart

H2 FlowStop

PlatesRelease

3 mm cell

Pchamber(start) ～ 10-5 Torr

Average thickness 2.7 mm

Measurement of thickness

ExperimentProton elastic scattering

Density distribution of unstable nucleiDensity distribution of unstable nuclei

RI beam

NaI array

MWDC

Vacuum chamber

Window less solid hydrogen

Si Chamber

Beam tracker

Recoil Proton: 1 ～ 100 MeV

Energy resolution < 600 keV(FWHM)

RI beam: 200 – 300 MeV/A

t = 1 mm

Summary

We have developed small solid hydrogen target system.We have developed small solid hydrogen target system.

1: Solid hydrogen target with thin film d = 30 mm, t = 3 mm, Mylar 25,50μm

Clear solid hydrogen target without void.Thickness measurement.

2: Windowless solid hydrogen target d = 30 mm, t = 3 mm

Clear solid hydrogen target without void.Thickness measurement.10 days operation

Next step: More thinner window less target, t = 1 mm