Construction of Laser-Electro-Photons (LEPS) at Taiwan Photon Source (TPS)

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Construction of Laser-Electro-Photons (LEPS) at
Taiwan Photon Source (TPS)

• Wen-Chen Chang
• Institute of Physics, Academia Sinica

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Outline

• Design parameters
• Physics motivation
• Experimental setup
• Cost estimation

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Laser-Electron-PhotonS facility
3.3 GeV electron
Backward-Compton scattering
Recoil electron
Collision
Tagging counter
a) Storage Ring
Laser light
Energy spectrum of BCS photons Bremsstrahlung
Compton g-ray
b) Laser hutch
c) Experimental hutch
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Summary of Existing LEPS Facilities Worldwide
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Backward-Compton-Scattering Spectra using 266nm
Laser
Minimum photon energy for production
Energy of Electrons
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Photon Flux
Laser and electron Laser Wavelength Output Power Repetition Rate Pulse length Electron Current Energy Photon Flux Emax
SPring-8 Paladin 355 nm 8W 80MHz 5ps 100mA 8 GeV 700 KHz 2.5 GeV
TPS AVAI 266 nm 3W 100KHz 25ns 300mA 3.3 GeV 1.2 MHz 0.6 GeV
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LEGS Exp in BNL
The LEPS facility according to the current
parameters of TPS is most similar to the LEGS
exp in BNL, which was shutdown at the end of year
2006. The beam time using polarized HD target in
LEGS was rather limited. The polarization degree
was not high P(H)60 and P(D)16.5.
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Physics Program

• High precision measurement of ?N??N and ? N?? ? N
  with polarized photon beam and polarized targets.
  This will provide the data on the
  double-polarization variables E and G, as well as
  beam asymmetry, and cross section data for the
  neutron and the proton. The data are extremely
  important information for the low-energy GDH
  integral sum of these two reactions.
• Magnetic dipole moment of Delta(1232)

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Motivation

• Constructing a LEPS beamline in Taiwan is no
  more than a duplicate LEGS experiment at BNL IF
  WITHOUT POLARIZED TARGET. As mentioned before,
  the beam time with polarized target and
  comprehensive detectors in LEGS Exp was rather
  limited (about 2 months in year 2006).
• However recently we learned there is a big
  progress in developing the polarized HD target in
  Osaka University and the whole technique will
  become available in about 2-3 years. We start
  participating in this project. The combined use
  of high-degree polarized photon beam and HD
  target will bring up the extremely interesting
  physics program.
• The competition will come from the MAMIC at
  Mainz. The schedule of operation will be within a
  few years. However their focus is mainly on the
  high-energy side for strangeness meson
  production.
• We have the advantage of inheriting the
  experience and hardware from the LEPS experiment
  in Japan.

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Experimental set-up

• Tagged photon beam M ?lt E? lt500 MeV Flux 1
  MHz.
• High-degree Linearly polarized photons P(?)gt95.
• Polarized HD target P(H)90P(D)60.
• Large acceptance detectors
• Time Projection Chamber charged pions. One is
  available at LEPS experiment and we can consider
  reuse it in Taiwan.
• Photon detector photon and neutral pions. It
  needs to be constructed.

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Dilution refrigerator
Leiden Cryogenics DRS-3000 (He3-He4) Cooling
power 3000µW at 120 mK Lowest
temperature 6 mK Magnetic Field
17 T Homogeneity of Magnetic Field 510-4
for 15 cm
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IBC(In Beam Cryostat) for BL33LEP
2.5cm
Al wire
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Cost Estimate

• Laser 200K USD / per unit.
• Target Polarized HD target 1M.
• Time Projection Detector 50K (if we cannot
  reuse the current one in LEPS).
• Photon Detector crystal ball with 4? coverage,
  is 300K 500K. (This might be an optional
  choice at the every beginning.)
• Electronics 500K.
• In total about USD2.2M.