Overview of SHARAQ spectrometer -- commissioning · Overview of SHARAQ spectrometer --...
Transcript of Overview of SHARAQ spectrometer -- commissioning · Overview of SHARAQ spectrometer --...
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.