OUTLOOK ON FLUKA SIMULATIONS FOR UDULATOR DAMAGE AND BLM RESPONSE

1. Mario Santana Leitner, Alberto Fassò and Joachim Vollaire Radiation Protection Department Stanford Linear Accelerator Center LCLS Beam Loss Monitor Preliminary Design Review SLAC, January 24, 2008 OUTLOOK ON FLUKA SIMULATIONS FOR UDULATOR DAMAGE AND BLM RESPONSE

2. Outline • Characterization of demagnetization under radiation fields • Radiation showers along the undulator • Beam loss monitor response and correlation to losses in the undulator

3. Characterization of the demagnetization LCLS Permanent Magnet Damage Study; experiment T493 Experiment spokesman: by Heinz-Dieter Nuhn SLAC Experiment (9 Nd-Fe-B Samples, 13.7-GeV electron) FLUKA geometry

4. Characterization of the demagnetization Measured Damage Not Proportional to Dose • Dose calculated and demagnetization measured are for the whole sample • Difference between forward and side samples

5. Characterization of the demagnetization Dose Fraction and Neutrons Neutron fluence in all samples Sample 1

6. Characterization of the demagnetization Mapping of 2-D Neutron Fluence in Samples

7. Characterization of the demagnetization Mapping of Measurement of 2-D Demagnetization Demagnetization measurements analyzed by Heinz-Dieter Nuhn

8. Characterization of the demagnetization New FLUKA simulations to match demagnetization grid The geometry of the magnets has been re-written to match the detector scoring with the virtual sub-regions - 800 detectors for the fluence - Region bin-size 2mm x 2mm Simulations to be sent now Analysis of the results requires some time

9. Radiation showers along the undulator FLUKA model of LCLS LCLS model including detailed description of the segments, dumps, magnets, magnetic fields, etc. BLM array just introduced.

10. Radiation showers along the undulator Magnetic field test. Electron transport. 30 micron displacement in X or Y plane. Further analysis ongoing…

11. BLM coarse geometric implementation done. - Array of BLM’s at 40 cm from following segment - thin W radiator in the front. What should be the thickness? - What is the thickness of the aluminum wall in the inner surfaces? FLUKA scoring subroutines to be written. Other FLUKA options to be examined. BLM response simulation and correlation to losses in the undulator Biasing destroys correlations: therefore for this option it is necessary to run FLUKA in analog mode. Since

12. CommandDETECT We call an"event" the energy deposited in a user-defined set of one or moreDETECTORREGIONSby one primary particle and by its secondaries. We call a "signal" the energy deposited in a user-defined set of one or moreTRIGGERREGIONSby the same primary particle and secondaries. Output: a distribution of energy deposited per event in the DETECTOR REGIONSin coincidencewith a signal larger than a pre-defined cut-off Possible application: to find correlations between dose in BLM and dose in a set of magnets FLUKA features for BLM simulations Biasing destroys correlations: therefore for this option it is necessary to run FLUKA in analog mode. Since

13. FLUKA features for BLM simulations Quenching and Optical Photons QUENCHING:FLUKA can calculate energy deposition in scintillators corrected for quenching, applying the Birks law. This can allow to predict the correct BLM response in a mixed radiation field of photons, neutrons and other particles OPTICAL PHOTONS: FLUKA can also produce and transport scintillation light if the user provides the wavelength.