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SNS Laser Wire Final Design Review

SNS Laser Wire Final Design Review. Diagnostic Groups: BNL, LANL,LBNL And ORNL Collaborators: SLAC, FNAL Presented by Saeed Assadi. July 23-25, 2002. Outline:. Progress Report. 2) Summary of the collaboration Since May-20-2002 Presentation.

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SNS Laser Wire Final Design Review

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  1. SNS Laser Wire Final Design Review Diagnostic Groups: BNL, LANL,LBNL And ORNL Collaborators: SLAC, FNAL Presented by Saeed Assadi July 23-25, 2002

  2. Outline: • Progress Report. • 2) Summary of the collaboration Since May-20-2002 Presentation. • 3) Measurement results from MEBT and BNL 200 MeV line. • 4) Electron detection, magnet design, transport layout and more • 5) What’s Next

  3. Multi-National Laboratory Diagnostic Collaborators Tom Shea, Sasha Aleksandrov, Saeed Assadi, Willem Blokland, Craig Deibele, Warren Grice, Ted Hunter, Danny Mangra, Dave Purcell, Dan StoutDavid Purcell ORNL Peter Cameron, Roger Connolly, Craig Dawson, Chris Degen, Sheng Peng, Marty Kesselman, Bob Sikora, BNL Mike Plum, John Power, Bob Shafer, Jim Stovall LANL LBL Larry Doolittle, Darryl Oshatz, Alex Ratti Joe Frisch , Keith Jobe, Marc Ross, Jim Crisp (FNAL), Bob Webber (FNAL) SLAC

  4. Present Baseline Diagnostics Dave Purcell

  5. Proposed Laser Wire Installations 402.5 MHz 805 MHz HEBT MEBT To Ring and TGT DTL CCL SRF, ß=0.61, 0.81 RFQ Injector 1000 MeV 86.8 MeV 186 MeV 2.5 MeV 380 MeV MEBT 5 WS (elec. only) 6 BPM (elec. only) 2 Sl&Col (act. only) DTL 5 WS 10 BPM 6 CM (p/u only) 5 ED/FC D-plate (7.5 MeV) 1 WS 3 BPM 1 CM (p/u only) 1 ED/FC 2 Sl&Coll emit 1 Phosphor screen 1 8 seg. halo scraper 1 Beam stop / F-Cup CCL 8 WS 12 BPM 2 CM (p/u only) 1 ED/FC SCL 32 WS (16 elec.) 32 BPM HEBT 3 WS (dumps) 22 BPM (elec. only) RTBT 1 Harp Laser Wires Key WS = wire scanner BPM = beam position monitor Sl&Col = slit and collector emittance station CM = current monitor ED/FC = energy degrader & Faraday Cup

  6. Why Choose Laser-wire over Conventional Wire? Conventional Wire • Requires off-operation with 100 ms macro-pulses at low rep rate • Ablation from the wire may contaminate the SRF cavity • Signal to noise not a problem • Maintenance requires vacuum access • Very radiation hard Laser Wire • Minimal impact on normal operation • Virtually no impact on SRF cavities or vacuum • Low signal to noise ratio but using electron collector works • No parts inside the vacuum • Radiation hard @ l<1500nm

  7. Recent Progress: • Better data set from 200 MeV beam at BNL. • Conventional wire data v.s. laser-wire from BNL 200 MeV is obtained. • More refined data is obtained from MEBT. • More advanced data analysis. • Electron detector is designed • Dipole magnet is designed and under construction • Vacuum beam box is designed and is being detailed for manufacturing. • Tunnel optics box design is being detailed. • Penetration access to tunnel is constructed • We have started setting up a laser room at RATS. We have received two free laser tables. • We are in a process of buying parts for Oct-02 studies.

  8. Progress Report Since May-20-2002: 1) Electron collector design is complete. 2) Magnet design simulation is complete. Detailing of the magnet is complete. The magnet is sent for prototyping. 3) Vacuum beam box design is 80% complete. 4) Data acquisition: EPICS is installed on the oscilloscope, Runtime LabVIEW is running on the scope. Shared memory is running on the scope and serving data. 5) What’s Next

  9. What does the Laser do? Photo-neutralization H0 + e H- hn • Requirements • High peak power • Small spot size • Transverse scan • Temporal stability • Detection Cross-section is well known therefore stripping efficiency calculation is a matter of algebraic manipulation (tech. notes)

  10. Calculated stripping efficiency r [%] It is safe to assume stripping efficiency of 15% Nominal emittance 2 x Nominal emittance H- time Ibeam % of Ibeam 12ns

  11. Calculated efficiencies at 400 MeV

  12. To speed up the laser wire data acquisition, and analysis, we are integrating EPICS and LabView in the scope and serve the results to users.

  13. More Refined Data Acquisition, Better Data Analysis MEBT laser Profile and fit Raw data is Sent through A LabView program for further analysis

  14. BNL 200 MeV line data swire=5.7mm and sLPM=6.69mm Carbon Wire [RED] Laser Wire [Blue] • Reasons for the difference in measured width? • The width of the laser beam should add 0.3mm, • 2. The laser energy is drifting slowly.

  15. We will not use the original SCL beam box due to cost SCL

  16. Raft design will not change with the new laser box.

  17. Detection of released electrons • Advantages: • large number of electrons • charge integrating amplifier similar to BLM • Energy of electrons is well defined • Electron beam is well collimated • Drawbacks • External magnets are required • In vacuum collectors are required • Might suffer from beam loss background } good S/N } easy to collect

  18. Signal strength (number of electrons x 108) for 20mA beam Nominal emittance 2 x Nominal emittance It is safe to assume number of released electrons of 2·108 U = 2e8*1.6e-19/12e-9*50 = 133mV on 50 Ohm load (laser at beam center) Bending magnet Laser beam Electron collector

  19. 3-D model of the electron detector is complete and 60 dB or noise (rf) rejection is obtained

  20. We expect to measure 120 mV from electron collector at 38 mA, expected noise is about 1 mV (-60dB– Green Curve).

  21. 3-D view of the SCL BPM and the electron detector electrode

  22. 3-D view of the SCL BPM and the electron detector assembly

  23. Required Magnetic Field to Collect Electrons in SCL: Choosing: • Required magnetic field spans from 70Gs at lowest energy to 190Gs at the linac exit. As beam energy can deviate from design values during commissioning/operation it is desirable to have magnets with variable field. • Note that electron detector been discussed is not an imaging device therefore high quality of the field is not required. • Deflection of the ion beam is negligibly small an can be corrected by baseline steering correctors therefore no compensating magnet is required.

  24. Magnet assembly

  25. Schedule and Goals

  26. Schedule and Goals

  27. SCL Warm section: Laser ports, magnet and the electron detector is shown

  28. To calibrate and evaluate the electron detector, we will use two BCMs

  29. Cross Section of Optics Line in the Tunnel Optics Pipe

  30. Location of the Laser Room in the HEBT Area • Advantages of a single laser • Laser expense shared between stations • Laser not exposed to radiation Laser Room

  31. Laser Transport from HEBT Service Area to the Tunnel

  32. Transport Line Warm Section HEBT

  33. Transport Line Modular Design HBET Service Building LINAC tunnel • Boxes secured to building walls, ceilings, etc. • Designed to accept a variety of optical components • Cable feedthroughs • Pipes mounted between boxes

  34. Beam Pick-offs The beam will be diverted from the main line by a pneumatically driven stage. OFF ON

  35. Optics Box under consideration Laser Wire

  36. Optical Layout is underway: Layout 66-80 mm 60-74 mm 120 mm 90 mm

  37. Maximizing the scanning range 35 mm

  38. Variable ratio of H-minus to laser beam size Adjustable Spot Size Lens translates 14 mm Spot size ranges from 10 µm to 2 mm

  39. Spot sizes and peak energy densities for 200 mJ pulse Lens d = 25.4 mm U = 0.16 J/cm2 Mirror d = 25.4 mm U = 0.11 J/cm2 Entrance window d = 15.0 mm U = 0.22 J/cm2 Exit window d = 12.7 mm U = 0.28 J/cm2 Damage threshold ~ 5 J/cm2

  40. Position of mirror, lens and windows Reflected Beams Reflected beam diverges harmlessly. Reflected beam comes to a focus upstream of pick-off mirror.

  41. Schedule FY 02 FY 03 FY 04 FNAL Study Design and Build Prototype (16 ManMonths) Software Development (6 ManMonths) Design Transport Components (2 ManMonths) Fabricate Beam Boxes (5 ManMonths) Fabricate Transport Components (2 ManMonths) Laser Room Construction (2 ManMonths) Transport Line Installation (3 ManMonths) Equip Laser Room (1 ManMonths) Safety System Installation (2 ManMonths) Transport Beam Alignment (2 ManMonths) Final Installation and Verification (18 ManMonths) Total Effort: 4.9 ManYears

  42. Schedule and Goals • Magnet design will be completed by July-22-2002, request • for cost estimate will go out by the end of July. • Complete the electron detector drawing and sent to the shop • (August-10-2002) • Complete the beam box by August-10-2002. Send for prototype • on August-20-2002. • Refine the data acquisition and analysis programs (Aug-30-2002). • Verification of the new laser beam detection at BNL’s 200 MeV line • (October-2002). • 6) Collaborative effort on testing laser wire at FNAL (October-2002).

  43. Schedule and Goals 7) Electronics design just started. We are relying on off the shelf components such as LeCroy charge collector module. 8) In tunnel laser-optics box is started. Various mounting schemes are under considerations.

  44. Backup Material is posted on the web http://www.sns.gov/diagnostics/documents/Lasermain.htm

  45. Proposed Laser

  46. Laser Wire Dipole Field Lines

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