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Research Activity of Electron Beam User Using 2.5 GeV Linac at Pohang Accelerator Laboratory

Research Activity of Electron Beam User Using 2.5 GeV Linac at Pohang Accelerator Laboratory. 2003. 8. 28-29. Contents. 2.5 GeV Electron Linac Electron Beam User Facility Research Activities using 2.5 GeV Electron Linac Double Differential Photoneutron Yield Measurements

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Research Activity of Electron Beam User Using 2.5 GeV Linac at Pohang Accelerator Laboratory

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  1. Research Activity of Electron Beam User Using 2.5 GeV Linac at Pohang Accelerator Laboratory 2003. 8. 28-29

  2. Contents • 2.5 GeV Electron Linac • Electron Beam User Facility • Research Activities using 2.5 GeV Electron Linac • Double Differential Photoneutron Yield Measurements • Radioactivity Measurements in Target Material • E-beam Effects on NbFeB and SmCo Magnets • Radiation Damage Test of Multigap Resistive Plate Counter • Detection Technique Developments of Illicit Material • Electron Beam User Committee & Summary

  3. 2.5 GeV Electron Linac • Nominal Energy : 2.5 GeV, Energy spread : ~ 0.3 % • Beam : 1 nsec in pulse length, 10 Hz in pulse repetition rate • Beam size : 1 cm (W) x 0.5 cm (H) at the targets • Electron intensity : 0.5 ~ 5 nC/sec at the targets The accuracy (~10 %) was verified to by the activation analysis using Au-foil and GDR reaction • Normal operation as a injector of storage ring : Twice a day (15 min for each injection) The other time ? Photo-neutron Source • Using energy-analyzed beam line • Short pulsed neutron beam for TOF experiment • Two target systems : I – the concrete cave with 1 x 1 m2 cross-section, II – the concrete hutch with 1.5 x 2 m2 cross-section and 2 m length • Three flight paths for TOF experiment : 10.4m (900), 8.1m (1400), and 6.9 m (480)

  4. Electron Beam User Facility at the beam dump area of 2.5 GeV linac Fig. 1. Target area in tunnel and the detection room on the ground.

  5. Photoneutron measurements from targets (PAL, KEK, Kyoto Univ., JAERI) H.S.Lee et al., J. Nucl. Sci. & Tech. Suppl. 1, 207 (2001) T.Sato, et al., Nucl. Instr. & Meth. A463, 299 (2001) H.S.Lee et al., J. Nucl. Sci. & Tech. Suppl. 2, 1228 (2002) • Differential photoneutron production yields at 90 degree • Fast time-of-flight system with Pilot-U • (BC418) scintillation detector • Dependence of yields on target condition : • target atomic number and thickness • Targets : • C, Al, Ti, Fe, Cu, Mo, Sn, W, Pb, Bi • Size = 5 cmx 5 cm • Thickness = 0.5~10 r.l. Fig. 2. Experimental setup.

  6. Target En > 20 MeV En < 20 MeV Bathowa This workb Bathowa This workb, c Cu 0.013 0.013 0.35 0.19 Sn 0.011 0.21 Pb 0.009 0.0079 0.41 0.28 Photoneutron measurements from targets (PAL, KEK, Kyoto Univ., JAERI) Table 1. Number of neutrons produced per 1-GeV primary electron in thick targets (10 r.l. thickness). a) Estimated value by Dinter based on the measurements by Bathow b) Neutron yields at 90 degrees were multiplied by 4 π c) Yields between 2 and 20 MeV. Fig. 3. Differential photonuetron yields from Sn targets with the thickness of 1 to 10 r.l.

  7. Photoneutron measurements from targets (PAL, KEK, Kyoto Univ., JAERI) Semi-empirical formula I to calculate differential yields at j-th energy bin - Neutron produced by hadron cascade was considered through the term, DA1/3. - C & D, were calculated by least square fitting to measured yields. Fig. 4. Z-number dependence of differential yields, as a function of neutron energy, from six targets of about 1 r.l. : Al(1.0 r.l.), Ti(0.983), Cu(0.979), Sn(1.0), W(1.0), Pb(0.89). Lines are results which are fitted with Eq.(4).

  8. Photoneutron measurements from targets (PAL, KEK, Kyoto Univ., JAERI) Semi-empirical formula II to calculate differential yields at i-th thickness and j-th energy. - Neutron produced by hadron cascade was considered too. - C1 & D1, were calculated by least square fitting for measure yields. Fig.5. Target thickness dependence of differential yields (in Fig. 5) from Sn targets, as a function of neutron energy. Lines are results which are fitted with Eq. (6).

  9. In-Tunnel Measurements To measure the angular distribution of photoneutron yields Serious dark currents problem was solved

  10. Angular Characteristics of DD Yields(PAL, KEK, Kyoto Univ., JAERI) H.S. Lee, et al., presented at ISORD-2 (2003) • No distinctive trend depending the target elements ! • DD Yield decrease at backward direction is more serious. • DD Yields at lower energy looks following isotropic property. (Pb) (Sn) (Cu) Fig. 6. Angular characteristics of double differential photo-neutron yields from about 10 r.l.-thick Cu, Sn and Pb targets for three angles and the calculated yields by using EGS4 + PICA3.

  11. Radioactivity in Low-Z materials (KEK, Kyoto Univ., JAERI, PAL) S.Ban, et al., J. Nucl. Sci. & Tech. Suppl. 2, 1191 (2002)

  12. E-beam effect I on NdFeB and SmCo(SPring-8 & PAL) Demagnetization Study of undulator magnets irradiated with 2 GeV electron beam Bizen et al., Nucl. Instr. & Meth. A 467, 185 (2001) Fig. 7. The irradiation arrangement and the in-situ measurement system of magnetic Field. Fig. 8. The normalized maximum magnetic field change of each magnet in the different stacking number of the magnets as a function of the accumulated electron dose. The magnet position in the stack is labeled 1 st, 2 nd, 3 rd et al from the upstream. (NdFeB Case)

  13. E-beam effect I on NdFeB and SmCo(Spring-8 & PAL) Bizen et al., Nucl. Instr. & Meth. A 467, 185 (2001) • Other processed or ongoing research subjects : • Dependency on manufacturing method • (different manufacturer) • Dependency on pre-thermal treatment • Dependency on NdFeB and SmCo • Dependency on magnetic field direction Fig. 9. The normalized magnetic field change of the 2 nd magnet on the perpendicular direction to the electron beam.

  14. E-beam effect II on Nd2Fe14B(PAL & POSTECH) X-ray Absorption Properties Magnetic Properties Consistent with the demagnetization effects observed in undulator magnets ! Bizen et al., Nucl. Instr. & Meth. A 467, 185 (2001) No appreciable changes in local structure !

  15. Radiation Damage Test of MRPC (INFN-Bologna, CERN, Kangnung Univ., PAL) Performance test of Multigap Resistive Plate Counter The current and the single rate have been reduced after irradiation, whereas the efficiency does not show any significant change.

  16. Detection Techniques of Illicit Materials (PAL, Ulsan Univ.) Neutron imaging techniques using transmission spectrum of pulsed fast neutrons to estimate amounts of C, N, O in illicit materials Total cross-sections of C, N, O measured in this experiment and in ENDF-VI library. Experimental setup for detection of illicit material.

  17. Operation Parameters PHERF (2.5 GeV linac) Test Linac Beam Energy (MeV) 2000 ~ 2500 50 ~ 80 Pulse Width (nsec) 1 ~ 1.5 3500 Pulse Repetition Rate (Hz) 10 10 Beam Intensity ~ 1E+11 per second 100 mA Electron Beam User Committee • The two electron linacs, 2.5 GeV linac(PHERF) and Test Linac, are normally available for electron beam users about 180 days a year according to Synchrotron Radiation Beam Schedule of the Pohang Light Source. • The PAL Electron Beam User Committee has issued two times a year for all user and scientific communities to apply the beam time. • These applications are accepted through the standard peer review by the committee and the safety peer review. Forms and instructions can be found at PAL homepage • Contacts and General Inquires : Hee-Seock Lee lee@postech.ac.kr, 054-279-1854

  18. Summary • Pulsed photo-neutron source was developed by using 2.5 GeV electron linac. • The basic data for the radiation shielding of high energy electron accelerator was obtained : Differential photo-neutron yields. • Several application researches have been carried out successfully. • 0.05 ~ 0.5 nC/pulse, 10Hz, 1 nsec beam is available. • Two target zones are available for energy-analyzed electron beam. • Application using electron beam is opened for any persons and any research.

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