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Piotr Bednarczyk 1,2 and Adam Maj 2 for the RISING Collaboration

Remarks on the background g radiation in the RISING fast beam campaign *. Piotr Bednarczyk 1,2 and Adam Maj 2 for the RISING Collaboration. 1 GSI Darmstadt, Germany 2 IFJ PAN Kraków, Poland. * ) Based on discussions with and contributions from:

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Piotr Bednarczyk 1,2 and Adam Maj 2 for the RISING Collaboration

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  1. Remarks on the background g radiation in the RISING fast beam campaign* Piotr Bednarczyk1,2 and Adam Maj2 for the RISING Collaboration 1GSI Darmstadt, Germany 2IFJ PAN Kraków, Poland *) Based on discussions with and contributions from: A.Bürger(Bonn),F.Camera (Milano), P.Doornenbal (GSI), J.Gerl (GSI),M.Górska(GSI),M.Kmiecik (Kraków), Zs. Podolyak(Surrey), M. Taylor(York),H.J.Wollersheim (GSI),Q. Zhong(Legnaro) HISPEC/DESPEC MEETING Valencia (Spain) 15th-16th June

  2. Layout of the fast-RISING experiment CATE: Position Sensitive Calorimeter Telescope FRS EUROBALL 15 cluster Ge-detectors HECTOR 8 BaF2 scintillators Relativistic Coulomb E2 or E1 excitation of projectile, break-up POV-Ray animation: R. Maj

  3. HECTOR SPECTRA

  4. Hector time spectra (100 MeV/u 84Kr beam) 142o 142o 142o 90o 142o 142o 142o Floor Tot

  5. Prompt (target) 5 ns before 15 ns after (CATE) 8-12 ns after

  6. 100 MeV/u 84Kr beam 142o 90o

  7. 90o 142o Simple wall Thick (0.2 g/cm2) Au target, 150 MeV/u 132Xe beam 90o 142o At the very beginning…

  8. 37Ca beam @196MeV/u; A/Q - 37Ca, CATE -Ca A/Q - 37Ca, CATE -K (mainly36K)

  9. Prompt radiation from target, increasing with the target thickness Early gamma radiation, coming from the beam line, caused by the light particles, ranging to very high energies (0-20 MeV) Late gamma radiation (neutrons?) Gamma radiation from the interaction of heavy ions in CATE Conclusions

  10. Ge SPECTRA beam MINIBALL detectors 15*7 crystals Ge Cluster detectors Target chamber CATE BaF2 HECTOR detectors

  11. 510 596 834 1014 1040 846 10000 1461 1369 1809 2614 2211 3004 1000 1000 2000 3000 A single gamma spectrum, no condition; 86Kr primary beam, 100MeV/u 54Cr secondary beam on Au target • Natural radioactivity: 40K, 208Pb,… • 27Al,56Fe(n,n’) with fast neutrons, Doppler broadened • 27Al(p,2p)26Mg; with Ep~Ebeam/u • Ge n capture

  12. 55Ni@165 MeV/u Be-target; gates on CATE 129Sn@165 MeV/u Be-target; gates on CATE

  13. delayed n induced 350 50ns Coulex target, projectile prompt 27Al(p,2p)26Mg off-time, random Radioactivity lines 400 800 1200 1600 2000 2400 Time structure of an in-beam Ge spectrumselection: 132Xe primary beam on Au target & Xe outgoing particle Conclusion : A lot of high energy particles (protons) is emitted in the fragmentation reactions

  14. 200 ms In-beam (spill-on) pre-amplified Ge signal Huge amplitude (>> 20MeV), overshooting signals due to charged particles directly hitting the Ge crystal (?) 2 V “normal” gammas If only low amplitudes accepted (DGF filtering) 1400 600 x 0.25 ns 4300 4300 4300 4300 4300 4500 4500 4500 4500 4500 4700 4700 4700 4700 4700 4900 4900 4900 4900 4900 5100 5100 5100 5100 5100 5300 5300 5300 5300 5300 In-beam Ge time distribution @ 1st EB ring

  15. 0 Ge multiplicity distribution 1 7 1 15 bad signals (satellite time peaks ) 5 clusters in the central ring good signals (central time peak position) Number of fired crystals in a cluster Number of clusters involved Conclusion:Radiation/particles of high energy irradiate several Ge detectors (mainly central) in the same time

  16. Zs. Podolyak et al, Nucl. Phys. A722 (2003) 273c Around: 196Os 200-201Pt 206Hg Surviving ions Destroyed ions

  17. 1400 600 4300 4300 4300 4300 4300 4500 4500 4500 4500 4500 4700 4700 4700 4700 4700 4900 4900 4900 4900 4900 5100 5100 5100 5100 5100 5300 5300 5300 5300 5300 Solution:Multiplicity filtering, when the number of crystals in a cluster is 1-3 (physically correct condition to detect the Compton scattering)

  18. 1400 600 3500 1500 11000 7000 3000 1850 1950 2050 2150 2250 A BaF2 (HECTOR) time distribution in coincidence with a cluster BaF-Ge MGe=1-3 Conclusion:the source of the high multiplicity, and high amplitude signals is situated downstream in the FRS area BaF-Ge MGe=5-7 BaF single Radiation emitted downstream neutrons target CATE

  19. Some other properties of the “bad” signals: • For the outer rings the number of saturated signals is reduced • With a primary beam (no fragmentation before a target) the bad signals contribute less • The higher beam energy and the current the bigger contribution of the bad signals • No matter if a reaction target is used or not A general conclusion on that point: A fragmentation in the FRS area is a source of the intensive background radiation seen by the Ge detectors. Its nature could be high energy particles* (protons) affecting mainly detectors close to the beam line. *However a pileup of several hundred gammas irradiating the whole array cannot be excluded (i.e. a very intense bremsstrahlung)

  20. Z A/Q Low energy background in a Ge gamma spectrum 134Cs secondary beam on Au target projectile in-fragments out 70 electron bremsstrahlung? 511 30 projectile in-out out 70 projectile Coulex Target Coulex 30 150 250 350 450 550 650 750 a few gammas, mainly elastic scattering=> enhanced background (correlated with a beam) gammas from excited fragments emitted in flight CATE

  21. Incoming-outgoing projectile selection, Au target ~600MeV/u 68Ni secondary beam ~100MeV/u 54Cr secondary beam ? 197Au Cx line(s~35mb) ~200MeV/u 132Xe primary beam 511 548 200 400 600 800 1000 1200

  22. 700 150 300 700 150 300 4600 4600 4600 4700 4700 4700 4800 4800 4800 4900 4900 4900 300 300 500 500 700 700 900 900 1100 1100 ~600MeV/u 68Ni secondary beam Gamma-energy • target • no target • difference Gamma-time Presence of the Au target enhances the prompt low energy gammas.

  23. 134Cs secondary beam g-single 3500 The prompt and delayed distributions are shifted in energy 1500 20 20 40 40 60 60 80 80 100 100 • prompt gammas • ~100nsdelayed 200 200 200 400 400 400 600 600 600 800 800 800 1000 1000 1000 132Xe primary beam g-single 14000 There is(almost) no prompt background bump if only a primary beam is of use 6000 200 200 200 400 400 400 600 600 600 800 800 800 1000 1000 1000 Spectra normalized according to the 400-1000 keV range

  24. 134Cs secondary beam g-particle MB Ring#4,5 ~90deg 350 150 110 EB Ring#2,3 ~30deg 70 30 35 EB Ring#1 ~15deg 15 40 80 120 160 200 240 Position of the (prompt) bump very little depends on a detector angle

  25. Zs. Podolyak et al, Nucl. Phys. A722 (2003) 273c At ~60 and~ 120 degrees

  26. Bremsstrahlung components • Radiative electron Capture of target electrons into bound states of the projectile • Primary Bremsstrahlung of target electrons produced by the collision with the projectile • Secondary Bremsstrahlung of high energy knock-out electrons re-scattering in the target • s (atomic) ~ 10000 * s (nuclear)

  27. Conclusion: • The prompt background may result from the (secondary ?) bremsstrahlung of electrons slowing down in the secondary target (Au). These electrons would be produced by fragments scattered on the FRS components. • (suppressed if there is no primary or secondary target) • The delayed component may be than related to the bremsstrahlung of the electrons in CATE (CsI) or in the environment. • (In this case the electrons could be also emitted from the secondary target)

  28. 132Xe (662 keV) v/c = 0.000 What happens to the spectral shape, when one applies Doppler corrections? „662 keV”

  29. 132Xe (662 keV) v/c = 0.100

  30. 132Xe (662 keV) v/c = 0.200

  31. 132Xe (662 keV) v/c = 0.300

  32. 132Xe (662 keV) v/c = 0.320

  33. 132Xe (662 keV) v/c = 0.330

  34. 132Xe (662 keV) v/c = 0.340

  35. 132Xe (662 keV) v/c = 0.345

  36. 132Xe (662 keV) v/c = 0.350

  37. 132Xe (662 keV) v/c = 0.355

  38. 132Xe (662 keV) v/c = 0.360

  39. 132Xe (662 keV) v/c = 0.370

  40. 132Xe (662 keV) v/c = 0.380

  41. 132Xe (662 keV) v/c = 0.390

  42. 132Xe (662 keV) v/c = 0.400

  43. 132Xe (662 keV) v/c = 0.410

  44. 132Xe (662 keV) v/c = 0.420

  45. 132Xe (662 keV) v/c = 0.430

  46. 132Xe (662 keV) v/c = 0.440

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