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“X-ray background in Miniball ”

“X-ray background in Miniball ”. Elisa Rapisarda Instituut voor Kern - en Stralingsfysica , K.U.Leuven for the MINIBALL, REX- and HIE-ISOLDE collaboration ( Work of the Summer Student Jean Baptiste Durrive ). Position in the hall. Present Shielding.

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“X-ray background in Miniball ”

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  1. “X-ray background in Miniball” Elisa Rapisarda InstituutvoorKern- en Stralingsfysica, K.U.Leuven for the MINIBALL, REX- and HIE-ISOLDE collaboration (Work of the SummerStudent Jean Baptiste Durrive)

  2. Position in the hall

  3. PresentShielding Note technique CERN-SC-2007-073-RP-TN EDMS No. 880127 v.1 Consolidation du blindage des cavités accélératrices « IH-structure » et « 9-gaps resonator » de REX-ISOLDE A. Dorsival

  4. 2006 Energy (keV) The three spectra below show the background without any concrete shielding (after the orange mobile lead shield was removed), with two layers of concrete and with the full shielding. It looks as though the detectors are still seeing quite a lot of Bremsstrahlung. We suspect much of this comes from the place where the beam line exits the 9-gap resonator, which is not really shielded by this concrete wall."

  5. Presently Experimentalγ-particle coincidence spectrum, background (random coincidence) subtracted Simulated GEANT 4 2+0+104Pd Counts (a.u.) 2+0+200Po • The actual background level in MINIBALL is “acceptable” • We would like to reduce it as low as possible • No random particle-gamma coincidences will be ideal !!!! • a factor 10 lower than the current level of the background

  6. New measurements of Background were performed in June AIM: Measurement of the absolute background in Miniball • varying the 9GAP power from 0kW to 85kW when LINAC ON and OFF • Varying the 9GAP power from 0kW to 85 kW when beam in the LINAC • With/without the 3 Pb layers, 1cm thick • HARD: • normalization to the Miniball solid angle • Estimation of Miniball efficiency (well know when source in target position) • Determination of X-ray spectrum due to the LINAC is possible thanks to the DAQ synchronized with the EBIS pulse (In-Beam and OFF-beam background are acquired) • Relative measurements and comparison possible • MORE: • Single Crystal, stand aloneHpGe from radioprotection group also used

  7. No Shielding, 84 kW in 9 GAP Per 1000 EBIS pulses IN Beam window (1ms) OFF Beam window (1ms) IN Beam minus OFF Beam 511 keV End Point 300 keV (Applied Voltage in 9GAP 400V Friderick)

  8. No Lead Panel Shielding Per 1000 EBIS pulses 84 kW 70 kW 55 kW 25 kW

  9. Lead Shielding .vs. no Lead Shielding 84 kW in 9 GAP, 1000 EBIS pulses Without Shielding With Shielding (three Pb panel 1cm thick each)

  10. X-rays Intensity .vs. 9GAP power

  11. Unfolding I … • NOTE: • We need to subtract the Compton continuum

  12. Unfolding II… • NOTE: • The experimental spectrum must be unfolded by the efficiency of Miniball • Miniball energy threshold around 40-60 keV depending on the cluster 84 kW in 9 GAP, with shielding

  13. GEANT4 simulation Source: 9GAP Detector thresholds not included in the simulation Assuming an approximate value of ε≈ 0.0015 % X-ray yields ≈ 107 per 1000 EBIS pulse per 4π Experimentally measured Source: Miniball target

  14. END

  15. HIE-Linac Installation Present 3 MeV/u 5.5 MeV/u 10 MeV/u 10 MeV/u 11/2014 4/2016 3/2017

  16. 3 experimental stations (2 installed in stage1) • TSR line and optional ‘car park’ line • Modular lattice • 8 lines: XL (REX Linac), XT00 – XT06 (REX Transfer) 5.5 MeV/u 10 MeV/u 15 MeV/u

  17. LINAC

  18. IN beam = EBIS 2010 OFF beam = no EBIS extra shielding around the beam line where it emerges from the bunker. extra shielding inside the bunker: on the front face (side nearest to Miniball)  Extra shielding between the 9-gap and the magnetic quadrupole BEN.MQ30 Sum of all Cores Energy (keV) The plot shows the hCoreSumIB spectrum (sum of all cores, calibrated in keV and gated on the in-beam window) minus the hCoreSumOB (the equivalent for off-beam).

  19. HIE-ISOLDE: three objectives • REX energy upgrade and increase of current capacity • Energy upgrade in three stages: 5.5 MeV/u and 10 MeV/u and lower energy capacity • REX trap and breeder upgrade • ISOLDE proton driver beam intensity upgrade 2 to 6 mA (linac 4) • Faster cycling of the booster • New target stations for ISOLDE • ISOLDE radioactive ion beam quality improvement • Smaller longitudinal and transverse emittance • Higher charge state for selected users • Better mass resolution • Target and ion source development e.g. RILIS

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