LEPS2: the second Laser-Electron Photon facility at SPring-8 RCNP M. Yosoi ・ How to increase the LEP intensity ・ Design of the main detector system ・ Polarized HD target
Beam line map of Spring-8 ~60 BL’s: atomic and molecular physics, material, biological and medical science engineering, Industrial use, etc.
Schematic view of the LEPS2 facility Backward Compton Scattering 10 times high intensity ： 8 GeV electron Multi laser injection & Laser beam shaping Recoil electron (future possibility: (Tagging) Re-injection of X-ray from undulator) Laser LEP (GeV γ -ray) Best emittance (parallel) beam ⇒ photon beam does not spread Large 4 π spectrometer based on BNL-E949 detector system. Beam dump Better resolutions are expected. New DAQ system will be adopted
Divergence of LEP beam LEPS2 LEPS BL31 < σ x’ >=14 µ rad. BL33 < σ x’ >=58 µ rad. e - e - Reaction region Reaction region Tagging point (7.8m) Tagging point (30m) Better divergence Better tagging resolution Smaller beam size at long distance
How to get the high Intensity Photon Beam We are aiming to produce one-order higher intensity photon beam : LEP intensity ≥ 10 7 cps for E γ <2.4 GeV beam (355 nm) ≥ 10 6 cps for E γ <2.9 GeV beam (266 nm) Simultaneous injection of 4-lasers [x4] Higher output power and lower power consumption CW lasers. 355 nm (for 2.4 GeV) 8 W → 16 W, 266 nm (for 2.9 GeV) 1 W → 2 W [x2] Laser beam shaping with cylindrical expander [x2] 400 um UV lasers laser (355/266 nm) 10 um pris expander m • Electron beam is horizontally wide. ⇒ BCS efficiency will be increased AR-coated mirror by elliptical laser beam. w/ stepping motor Need large aperture of the laser injection line reconstruct some BL chambers
Test of Laser Beam shaping with visible wavelength laser 40 mm Beam Shape Transformer 80 mm normal expander cylindrical expander Power density gets twice.
Design concepts of Main Detector Momentum resolution at forward angle ∆ p/p~1%. Good reaction tag. Large and smooth acceptance azimuthally Decay and polarization. Detection of decay product down to lower momentum 100 MeV/c Detection of neutral particle (Photon)
Main Detector Setup E949 Solenoid Magnet size: Φ 5m × 3.5m weight: ~400 t Field: 1.0 T Target cell γ CFRP SSD Target and Vertex detector
TOF TOP ・ PID sideway: TOF ( ∆ t =50 psec) forward: TOP (quarts Cerenkov)
Invariant Mass measurement
Polarized HD Target ・ We have developed the polarized HD target for these 6 years. ・ The proposed experiment is the ss-knockout measurement of the double polarization asymmetry of the Beam-Target double spin φ photoproduction, which is asymmetry at E γ = 2.0 GeV sensitive to the ss-bar content ss content 1% in nucleon through the ss-bar knockout process. (A.I.Titov et al. PRC58(1998)2429) 0.25% ・ When we succeed the 0% development and establish its technology, it will be a strong weapon at LEPS2.
Principle of polarized HD H and D are polarized by the static method, i.e., using the thermal equilibrium under the ultra low temperature and high magnetic field. Special advantage: After a few months aging time, spin is frozen, even under high temperature and low magnetic field. Longstanding effort at Syracuse, LEGS/BNL, ORSAY 10-20 mK 15-17T >80% for H, >20% for D (vector) 20% 70% in D with DNP
NMR signals after 53-day aging NMR Signal The first NMR spectra of polarized HD target. Aging time is 53 days under 17 T and 14 mK. Signal [mV] 19 F • As a result, relaxation time is more than 100 days at 300 mK and 1 T. H First day 1 day after 10 days after Signal [mV] F B(Tesla) B(Tesla) B(Tesla) Signal [mV] H B(Tesla) B(Tesla) B(Tesla)
Process to use in the experiment (120 km) Osaka Univ. RCNP Distillator SPring-8 LEPS(LEPS2) beam line γ DR : Dilution Refrigerator SC : Storage Cryostat TC1(2) : Transfer Cryostat IBC : In-Beam Cryostat
Dilution Refrigerator Transfer (DR) Cryostat @SP8 (TC2) 17 T Magnet Transfer Cryostat @RCNP (TC1) Storage In-Beam Cryostat Cryostat (IBC) (SC)
LEPS2 roadmap 2009FY 2010FY 2011FY 2012FY 2013FY E949 detector(BNL): Decompose Dismantl Assemble & partially transfer magnet magnet commisioning Spectrometer Construction of the main spectrometer Start full-scale experiment Detector design and forward spectrometer Detector R&D Submit High speed DAQ system Proposal experiment with 4 π photon detector Modify SR vacuum Beam Beam Partially start BL construction chambers pipe monitor R&D for high intensity missioning Laser injection system Beam com- Design & build the Infrastructure experimental bldg. Radiation shield 4 π photon detector (Tohoku ELPH) LEPS2 Polarized HD target: R&D and experiment at LEPS LEPS2 R&D of X-ray re-injrction system We need to get more budget and widen the collaboration.
2010.10.11
2010.12.10
Backup
Super Photon ring – 8 GeV • 8 GeV electron beam Russia China • Diameter ≈457 m Sapporo • RF 508 MHz North Korea • One-bunch is spread within σ ＝ 12 psec. Osaka South Korea Tokyo Nagoya • Beam Current = 100 mA • Top-up injection Osaka – SPring-8: about 120 km, One and half an hour highway drive.
LEPS new beam line (LEPS2) • Beam upgrade: Intensity --- High power laser, Multi laser(x4) --- Laser elliptic focus ~10 6 ~10 7 /sec for 1.5 GeV~2.4 GeV ~10 5 ~10 6 /sec for 1.5 GeV~2.9 GeV (Energy --- Laser with short λ , re-injected Soft X-ray+BCS (future possibility), up to ~7.5 GeV) • Detector upgrade: (reaction process & decay process) Scale & --- General-purpose large 4 π detector large experimental hutch Flexibility Coincidence measurement of charged particles and neutral particles (photons) BNL/E949 detector DAQ --- High speed for the minimum bias trigger • Target upgrade: Polarized HD target • Physics: Continuous study from LEPS (e.g. Θ + ), new Physics Workshop on LEPS2 (2005/7, 2007/1)
LEPS experiments (2000 – 2010) ye year ar 2000 2000 2001 2001 2002 2002 2003 2003 2004 2004 E_ γ < 2. Linea nearl rly P Polarized ed E < 2.4 G 4 GeV eV pho hoton b n bea eam BL co cons nstruct ruction & C & Comis issio ionin ing LH2 nucl nuclea ear nuclea nucl ear LH2, 2, L LD2 ( 2 (long ng) nucl nuclea ear t target ets (sho hort rt) ta targets ts ta targets ts target Gamma mma Fwd s spect ectro romet eter er Forw rward rd L LEPS s spect ectromet eter er det etect ector + TPC-I + T -I det etect ector Tagger (SSD→ScFi) year ye ar 2005 2005 2006 2006 2007 2007 2008 2008 2009 2009 2010 P E_ γ P E_ γ < 2. P E_ γ < 2. P E_ γ LP E LP E < 2.4 G 4 GeV eV LP E < 2.4 G 4 GeV eV LP E P E_ γ < 3 G LP E < 3 GeV eV < 3 G < 3 GeV eV (8W 8W P Paladin x n x2) 2) (test 16W Paladin) < 3 G < 3 GeV eV pho hoton b n bea eam (1W 1W S Sony ny) new t new targ rget et s system em f for T r TPC LH2 LD2, 2, L LH2 ( 2 (long ng) ( L LH2, LD2 LD2, LHe ) ) (lon ong) target Fwd s spect ectromet eter er Forw rward rd L LEPS s spect ectromet eter er Fwd Fw + TPC-I + T -II det etect ector dev evel elopment ent o of polarized ed H HD t target et
High Energy Backward Compton Photons
Backward Compton Scattering of X-ray for Ultra High Energy LEP Diamond mirror
Reaction mechanisms of φ meson photoproduction Diffractive production within the One-pion-exchange vector-meson-dominance model through Pomeron exchange >= > + > + = 2 2 | | | 1 p A uud B uuds s A B = 1 = j 0 j s s s s ss-knockout uud-knockout
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