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The Bifrost spectrometer

The Bifrost spectrometer . Progress STAP 2018 / 2 Rasmus Toft-Petersen Technical University of Denmark. Validating the McStas file with CAD (Martin Olsen). Backend from detector group ! (Milan Klausz). Analyzers Final arrangement. Cross talk shielding. Point-to-point make it simple.

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The Bifrost spectrometer

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  1. The Bifrost spectrometer ProgressSTAP 2018 / 2 Rasmus Toft-Petersen Technical University of Denmark

  2. Validating the McStasfile with CAD(Martin Olsen)

  3. Backend from detectorgroup!(Milan Klausz)

  4. AnalyzersFinal arrangement

  5. Cross talk shielding

  6. Point-to-pointmake it simple

  7. Validation of detailedgeometry

  8. Validation of detailedgeometry

  9. Performance is slightlystaggered

  10. Cave and tank Cd Lined Vac Tank 150mm Borated PE Beryllium Collimator Analysers Gamma Shielding (Cu) Cross Talk Shielding Detectors Rotational System

  11. Tank bottom

  12. Analyzer access

  13. Shielding Polyethyleneweight drives motion system design

  14. Cave (II)

  15. Cave (III) • Double layered, LEGO block construction • Working with Swedish company – C3C • Latest quote – 165k€ for design, manufacture and installation of cave walls (not including roof and penetrations) • Now working on the roof layout

  16. The Bifrost spectrometer Technical hot commissioning - Procedures and schedule Rasmus Toft-Petersen Technical University of Denmark

  17. Outline • Pre-hot commissioning • Chopper calibration • Monitor/flux validation • Normalization • Energy resolution • Q-resolution • Test-experiment(non-science)

  18. Outline

  19. Pre-hot commissioning Hot source detector/electronicscommissioningCheck the relationshipbetween gamma and neutron response, estimatethresholdsfor discrimination, check positioning resolution and triplet performance Check softwareMake sure detectorgeometry in Mantid is correct, make a simulated data set, reproducesimulated dispersion in Mantid. Check sample environment software, monitoring software etc. Make sure the magnet can go on Bifrost, and is controllable A couple of monthswork to be done in parallel

  20. Chopper calibration Openingprofile and chopper timing Fluence> 1012 n/s Monitor

  21. Chopper calibration Flux and overlap measurement

  22. Chopper calibration Opening time, timing, transport measurement

  23. Chopper calibration Overlap measurement, transport measurement, rise/fall times

  24. Monitors Weuse 4 monitors along the beamline, for guide diagnostics, chopper diagnostics and normalization N2 MWPC?Scintillators? MWPC? GEM? Fission?

  25. Monitor suggestions Nearmonolith: Fission chamber with low efficiency – 10^-8. Fast neutron flux from fission willbeinsignificant at 160 m. Shouldbeable to measure fluence of 10^12. Post-Bunker and post BW: Ordela monitors with nitrogen gas, efficiency of 10^-6 and max count rate of 10^6. Gamma sensitivitycomparable to neutron. May smere signal At sample: Either low efficiency for Day 1, or GEM type detectorsif the count rate cancomedown low enough. Wemight have a massivestability problem, which the ESS is lookinginto– largerthanwepresumed

  26. Chopper calibration Overlap measurement, transport measurement, rise/fall times Estimated time for chopper calibration:5 weeks (in total)

  27. Monitor and flux calibration • Gold foil for absolute flux. • Identifyaluminumbraggpeaks in monitor, maybe YIG sample before monitor • Use CF levels on knowncrystal to verifyintensityacross the frame.

  28. Monitor and flux calibration • Gold foil for absolute flux. • Identifyaluminumbraggpeaks in monitor, maybe YIG sample before monitor • Use CF levels on knowncrystal to verifyintensityacross the frame. Estimated time for monitorcalibration:2 weeks

  29. Normalization:Vanadium and CF levels Normalize for: Analyser reflectivity, spatial angle and incoming flux Scale resolution volumeand try to compareCF levels for differentanalyzersCompare CF levelintensitiesnormalizedby monitor and acccurrent, respectively

  30. Normalization:Vanadium and CF levels Normalize for: Analyser reflectivity, spatial angle and incoming flux Scale resolution volumeand try to compareCF levels for differentanalyzersCompare CF levelintensitiesnormalizedby monitor and acccurrent, respectively Estimated time for monitorNormalization:2 week

  31. Energy resolution:Vanadium and CF levels • Use vanadium to quantify the sizeand variance of elasticline widths • Usee.g. LiHoF4 to do the same in inelasticmodeUsecold chopper results to verify Prototype measurements on MARS @ PSI

  32. Energy resolution:Vanadium and CF levels Estimated time for monitorEnergy resolution:1.5 weeks • Use vanadium to quantify the sizeand variance of elasticline widths • Usee.g. LiHoF4 to do the same in inelasticmodeUsecold chopper results to verify Prototype measurements on MARS @ PSI

  33. Q-resolution:Vanadium and CF levels UseBraggpeaks to determine center widthand to verifydivergencejawsUsesteepmagnon to verify overall Q-resolution

  34. Q-resolution:Vanadium and CF levels Estimated time for monitorQ-resolution:1.5 weeks UseBraggpeaks to determine center widthand to verifydivergencejawsUsesteepmagnon to verify overall Q-resolution

  35. Test eksperiment:Known dispersion – MnF2?

  36. Test eksperiment:Known dispersion – MnF2? Two samples, Twosettings,Low flux4 weeks

  37. Total beam time requirements Chopper cascade: 5 weeks Monitor/normalization: 3weeks Energy resolution 1.5 weeks Q-resolution 1.5 weeks Test-experiments 4 weeksBackground 3 weeks ___________________________________ Perfect world total: 18 weeksAccelerator fudge (x1.2) Scientistfudge (x1.2)DMSC fudge (x1.1)Grand total : 28 weeks of beam time7-8 months

  38. The Bifrost spectrometer Early science and ressources Rasmus Toft-Petersen Technical University of Denmark

  39. Outline • Schedule • Day 1 capabilities • Early science: 4-spin plaquettes • Early science: Electricalfiels • Minimum day 1 requirements from SAD • Minimum day 1 requirements DMSC

  40. Rough access times E01: Oct - 19 E02/1: Oct - 19 E02/2: May - 21 D03 : Feb - 21 Bunker: August 21

  41. Critical dates Cave installation and fitout: Oct-19 – Jan-21 Guide/beamlineshielding installation: Jan-21-July 21 (ESS) Inbunker: Aug-21 – Oct-21Cold commisioning: 6 months (ongoingthroughout installation) BoT: July 22 Ready for science in early 23

  42. Day 1 capabilities

  43. Day 1 capabilities • 500 kW flux is 1.6 * 109 n/s/cm2-> factor of 5 on Thales • Assumeadding multiple Ef-mapstogether not straightforward.Single Efgain on Thales: x 5 • So ifonereallyneeds the mappingcapability, wehave a factor of 25 on Thales at 500 kW. • We have muchbetter resolution at similar flux. Wecan still doimpressivestuff, ifwestaydelocalized. Motivation: • Provethat Bifrost works, and producesmapping data sets thatcanbeeasilyanalyzed. • Entice the community to do ambitious sample environmentexperiments. • Stayaway from the high riskstuff

  44. Early science:4-spin plaquettes New quantum states in exoctic matter: a 4 spin plaquette M. E. Zayed, Nature Physicsvolume 13, pages 962–966 (2017)

  45. Twoplaquette types

  46. Twoplaquette types Mapping studies onvery small samples in pressure?Only on Bifrost. Wouldtakea while at 500 kW but wouldbefeasible (not at 100 kW)

  47. Electricalfieldmapping -only on Bifrost? E. LatagneHutubise, et al, PRB (2017) – theorypaper M. Bartkowiak, Rev SciInstr (2014)

  48. Minimum requirements The cost book value of the instrument is unchangedMoney is tight and wearedefining the mininumrequirements, stripping awaynice-to-haves Current ESS Future ESS

  49. SAD requirements • Weneed the 15 T magnet and orange 6 monthsbeforeready-for-beam-on-sample. Weneed to test magneticenvironment, sample handling procedure, etc, before neutrons • For early science, weneed a 20 kBarpressurecell, witha large sample space to demonstrate small sample performance. A dilutionfridgemaintained by SAD wouldbegood for wow-factorand proof of operation. (Q4 22) • Pressurecellshouldbetimed with 500 kW operation, dilutionmaybeusefulbefore.

  50. SAD summary 1) 15 T magnet and orange: Q4/21 2) Pressurecell: Q4/22 3) Access to dilutionstick: Q4/22 4) Electricalfields: Q1/23 Pressurecells and electricalfieldsmightbe in externalcollaborations. Only1) is essential for workhorse science Weneed to test the mounting and operation of sample environmentthatshouldbe done in coldcommissioning, ifpossible, and otherwiseduringshutdowns

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