Overview of SHARAQ spectrometer

-- commissioning --

H. Sakai

RIBF PAC meeting 20 November 2008

Under the Program

“Isospin-spin responses in CHarge-exchange exOthermic Reactions”

and

CNS, University of Tokyo

and

RIKEN Nishina Center

What is SHARAQ?   SHARAQ is a high resolution magnetic spectrometer for unstable (secondary) beam experiments.

  Grant-in-Aid of MEXT at 2005. (ICHOR program: H.S. spokesperson) initiative of University of Tokyo (UT)

  UT - RIKEN collaboration (joint venture).   SHARAQ spectrometer: UT

•  CNS •  Department of Physics

  Beam line + infrastructure : RIKEN

  Collaborations   SHARAQ: G. Berg(Notre Dam), A. Zeller(NSCL), Focal plane det.: P. Chomaz(GANIL) + … ; MOU(UT-GANIL)   ICHOR: R. Zegers(NSCL)

SHARAQ Characteristic

Energy resolution ΔE ～500keV for A=12、E/A=300MeV particle 0.5MeV/(300×12)MeV = 1.3×10-4

→　corresponds to momentum resolution of p/Δp ~15000

Angular resolution ⇔　momentum transfer resolution ex. 12N, 300MeV/A 9GeV/c CRITERION: Δq < 0.1 fm-1 Δq ～　p(beam)×Δθ →　　Δθ < 2 mrad Δθ = 1 mrad

•  QQDQD type •  Maximum rigidity 6.8 Tm •  Δp/p = 14700 •  Dispersion matching (x|δ), (θ|δ) •  Angular resolution < 1 mrad •  Solid angle 2.7 msr / 4.8 msr •  Rotatable (-2 to 15 degree) •  Weight 500 tons

target

Focal plane

matrix elements of SHARAQ

SHARAQ construction Field mapping

Vacuum chambers are being assembled Around the target pivot Focal plane chambers

1 m

High-resolution beam line for SHARAQ

Large momentum spread of RI beam 200 MeV/A 12Be beam with Δp/p = ±0.3% → ΔE ~ 30 MeV

Need a high resolution beam line !

ZDS

SAMURAI FH7

To be ready by the end of February 2009.

(lateral) dispersion matching for high momentum resolution angular dispersion matching for high angular resolution

Beam-line Operation Modes •  Dispersion matching mode

Best resolution, large target size •  High-resolution achromatic mode

Modest resolution, reasonable target size •  Large-acceptance achromatic mode

Low resolution, reasonable target size, large momentum acceptance (⇒high intensity)

Disp. match Mode Achromatic (large acceptance)

Resolution

Acceptance

Δp/p=1/15000 Δp/p=1/7500 Δp/p=1/1500 at target at F6 at F5

Δp/p = +/- 0.3 % Δθx= +/- 10 mr, Δθy= +/- 30 mr

Δp/p = +/- 0.3 % Δθx= +/- 10 mr, Δθy= +/- 30 mr

Δp/p = +/- 2 % Δθx= +/- 20 mr, Δθy= +/- 20 mr

Achromatic (high resolution)

BigRIPS

SHARAQ Beam Line

F3

Target

Matching conditions are satisfied. Symmetric design is introduced.

STQ10-11, STQ8-12, STQ13-S1 are symmetric. 19 DOFs for 34 Quadrupoles.

Y X

STQ7

STQ8

STQ9

STQ10

STQ11

STQ12

STQ13

DQ

STQ-S3

STQ-S1

STQ-S2

BM-S1

BM-S2

SQ1SQ2

F3

F4

F5

F6

Target

F-S1

F-S2

Δθx= +/- 10 mr, Δθy= +/- 30 mr, Δx = +/- 3 mm, Δy = +/- 3 mm, ΔP= +/- 0.3 %

Ion Optics (1st order): Disp. mode

FH7

FH8

FH9

F3

F6

F-H7

F-H8

F-H9

F-H10

F-H12

Big

RIP

S

DM

Bea

m L

ine

SH

AR

AQ

Beam Tuning Exp.

"

"

"

"

"

""

pout/PID

pF3 /Spot Size monitoring "

pbeam "

•  Confirmation of beam transport •  (x,y) and/or (θ,φ)

Experiment

Beam Tuning

•  pF3 : essential for DM correction •  pout: Reaction Q value •  pout-pbeam : Scattering Angle

Beam-line/SHARAQ focal-plane detectors

Detectors: beam-line : 6 sets focal plane : 1 set

“High resolution” achromatic mode

T. Kawabata

Δθx= +/- 10 mr, Δθy= +/- 30 mr, Δx = +/- 3 mm, Δy = +/- 3 mm, ΔP= +/- 0.3 %

F3 F4

F5 F6 FH7 FH8

FH9

target

Beam size < a few cm

Momentum acceptance is ± 0.3 %, keeping Δp/p of ~ 1/7500. ( F6)

1.56 0.00 1.36

0.00 0.64 0.00

0.00 0.74

0.00 0.36

same as diper. mode

“Large acceptance” achromatic mode

Δθx= +/- 20 mr, Δθy= +/- 20 mr, Δx = +/- 3 mm, Δy = +/- 3 mm, ΔP= +/- 2 %

F4

F5

F6 F3

F-H7 F-H8

F-H9

target Momentum acceptance can be increase up to ± 2 %.

resolution Δp/p~1/1500 (at F5 )

Beam transport is different from dispersion matching mode.

same as the standard BigRIPS transport up to F5.

Requirements of Tracking Detectors for dispersion matching

- Little disturbing of the beam Low Multiple Scattering: ~1 mrad (σ) Low Energy Straggling: < 1/1650 (Energy Resolution of BigRIPS)

- Precise measurement of the beam trajectory High Position Resolution: ~300 µm (FWHM) [ 30 cm*1 mrad ~ 300 µm ]

for using RI Beam - Overcoming of Low intensity

High Detection Efficiency → 100 % for light particles

for Beam-line detectors, especially - Operate under High Counting Rates → ~1 MHz

Drift Chambers with Low Gas Pressure installed at Beam line & Final focal plane of SHARAQ

Beam-line detectors

Tracking of beam (x,y,θ,φ,ΔE)

Low Pressure MWDC ( 5-20 kPa : d/LR<10-4)

Hybrid Readout for tracking Position ← Delay line readout of stripped cathode & Drift time to Anode wires

Effective area 　◎　Beam Spot Size of each focus 　　　(H×V, 3 patterns)

•  100×100 mm2 (photo)

•  150×150 mm2

•  200×150 mm2

Beam-line detectors (test with α beam)

•  Drift time-Position relation is consistent with simulation •  Position resolution of delay-line readout ~ 1.2 mm (FWHM)

Simulation

Drift time vs position (Delay line)

Drift time of an anode On-line beam image

after shaped slit (DL readout @5kPa)

Width corresponds to cathode position resolution

(~1.2mm)

Focal plane detectors

Detector Size

Cross section View

CRDC is being manufactured at GANIL now, and we start to check its performance soon

PID by TOF-ΔE-Bρ

Focal plane detectors (readout)

Anode: PreAmp+Discri → Timing signal (Y position) + Trigger of cathode readout Cathode: Multiplexered readout using GASSIPLEX chips

Buffer Format 1.2 µs Readout per 16ch(1 chip) (1600 + 50) ns Total (256ch) ~30µs

Needed Time

104 Hz ◎

Commissioning

March 2009 ~ GOAL of the commissioning:

1) establish high-resolution measurement with SHARAQ

2) examine feasibility of "first" experiments

ICHOR　Program （Grant-in-Aid of MEXT） Exothermic reactions

(12N,12C), (12B,12C), etc. first choice

RI beam production   Primary beam: 14N 250 MeV/A

max. intensity 250 pnA (assumed) AVF → RRC → SRC (IRC-skipping mode)

  Production target: 9Be 15 mmt

  Expected intensities (LISE++) for Δp/p=±0.3%: 12N 1.6×105 cps/pnA (max. 4×107 cps)

12B 2.8×105 cps/pnA (max. 7×107 cps) t 1.4×104 cps/pnA (max. 4×106 cps) 8He 480 cps/pnA (max. 1.2×105 cps) 10C 0.8×105 cps/pnA (max. 2×107 cps)

Task lists in the commissioning

  RI beam production Intensities and purities of RI beams Beam profile at F3

  Beam-line and Focal-plane detectors: Optimization: gas-pressure, high-voltage Detection efficiency for 12N, 12B, t, etc. Position and ΔE resolutions Rate dependences of the performances

  SHARAQ optics momentum resolution: (x|δ), (x|x) angular resolution: (a|a), (y|b), (y|y) other 1st order elements: (a|x), (a|δ) higher-order aberrations: (x|aa), (x|aaa), (x|aδ), . . . comparison with COSY calculations

Task lists in the commissioning (cont.)

Beam-line optics Dispersion matching mode F3 → Target: (x|δ), (a|δ), etc. higher-order aberrations to establish a tuning procedure

Achromatic beam transport (high-resolution) F3 → F6: (x|δ), (x|x), etc.　 　　　　　dispersive focal plane F3 → Target: (x|δ)=0, image size at target

Achromatic beam transport (large-acceptance) F3 → F5: (x|δ), (x|x), etc.

dispersive focal plane F3→ Target: (x|δ)=0, image size at target

Missing energy spectroscopy

PID tool of reaction products

Commissioning Plan

1st phase : Optics measurement (primary and secondary beams) plan(optimistic) for March-2009 run 0.5 days RI Beam production

2 days Detector and DAQ start-up 0.5 days SHARAQ optics measurement

1.5 days Optics measurement for dispersion matching mode 1 day Same for high-resolution achromatic mode

1 day Same for large-acceptance achromatic mode 0.5 days Background measurement

2nd phase : Feasibility test of exothermic reactions Event identification Background suppression (β-decays, charge states, etc) Energy and angular resolutions Feasibility test of triton-beam experiments (Z=1, high-rigidity beam, high intensity. . .)

Summary •  SHARAQ: magnets are ready vacuum chambers are being prepared •  High-resolution beamline:

being constructed, to be ready by the end of Feb. 2009 •  Detectors:

MWDC for BL: tested with a low-energy α beam CRDC for FP: constructed at GANIL → RIBF in Dec. 2008

•  Commissioning ： 　　　Establish high-resolution measurement with SHARAQ (optics meas. and dispersion matching technique) 　　　Examine feasibility of the "first" experiments (needed for ICHOR program)

→ first commissioning run is expected in March, 2009.