1. PXIE LEBT Status Update Lionel Prost PIP-II “Friday” Meeting January 16 th, 2015

2. Content Context and setup Performance Machine reliability Beam parameters stability Readiness for RFQ installation 2

3. Role of LEBT in PXIE Prepare beam for RFQ (i.e. ,  ) and machine protection DC operation  5 mA, reliable and ‘stable’   n,rms ≤ 0.25 mm mrad  Uncontrolled losses <10% Pulse operation  1-16667  s, 60 Hz  Twiss functions representative of DC beam operation  To transition from short pulse (commissioning) to DC (normal operation)  If not the same, DC Twiss functions should be predictable from short pulse measurements 3 Beam dump HEBTMEBTRFQ LEBT Ion Source HW & SSR1

4. Current setup All focusing elements, chopper, instrumentation have been installed except for the LEBT/RFQ Interface and its ‘scraper’  Also, most of the controls, PS… have been moved to their final location  The construction and installation of the bend has been delayed until FY16 4 DCCT Collimator Chopper Gate valve Emittance scanner Faraday Cup Water-cooled donut ~3.5 m T. Hamerla

5. Instrumentation Most of instrumentation is in place  4 electrically-isolated and water-cooled diaphragms  In first 2 solenoids; after kicker/absorber (a.k.a. collimator); in front of Faraday cup (a.k.a. donut)  Can be biased to tens of volts (and typically are)  Beam size measurements; Halo  DCCT following first solenoid  Measure accurately long pulses (1 ms and up)  IR camera  Beam spot monitor on absorber surface  Faraday cup at the end of the line  Toroid following the collimator  Emittance scanner  One direction only One more diaphragm to be added in front of the RFQ entrance (a.k.a. scraper)  Beam size measurement and RFQ vane protection 5 Only instrument not to be permanent (and its donut) Currently at the end of the beam line. Permanent location in IS vacuum chamber (plan for 2) Donut

6. Setup in picture 6 DCCT ‘Diagnostics’ box Water-cooled donut connectors Chopper assembly Gate valve Emittance scanner (not visible)

7. LEBT performance Demonstrated up to 10 mA, DC and pulse  Low uncontrolled beam loss (<2%)  Up to 60 Hz pulses   n,rms < 0.15 mm mrad  I Beam ≤ 5 mA (DC or pulsed) but ( ,  ) not matched to RFQ’s  Recent data indicate possibility of achieving low emittance with ( ,  ) close to target for RFQ Demonstrated chopping  Ion Source DC or long pulse (> 1 ms)  1  s to 16.6 ms pulses at 60 Hz 7

8. Machine reliability 8

9. LEBT reliability Conducted two 24-hour runs with nominal beam current (5 mA)  DC and chopped Main questions: Frequency of beam interruptions and stability of beam parameters  Experienced beam trips in DC mode during ‘regular’ shifts before Oct’14  None since (other than related to known/understood issues, e.g.: water trips)  Minimized current to extraction electrode  Increased remote operation capabilities  Remote power cycle the HV cabinet  Remote turn on/off the bias PS  Finite State Machines for monitoring  Currents (DCCT, FC, electrodes) are data logged; Twiss functions were measured a few times during long runs 9

10. 5 mA DC to Faraday cup for 24 hours without any trip  Had to install additional blocks and gates to close up cave during unattended operation (e.g.: at night)  Off-hours monitoring by Operators in MCR Setup ‘comfort’ displays Alarm blocks have been created Successful long run demonstration - DC (Dec. 17-18, 2014) 10 DCCT (0.5 mA/div) Faraday cup (0.5 mA/div) IS pressure (1e-5 torr/div) Extraction voltage (0.05 kV/div) 24 hours Interruptions due to measurements with emittance scanner i.e. not trips

11. 2 nd long run demonstration - Pulsed (Dec. 30-31, 2014) Demonstrate reliability of the modulators  10 ms pulse from the Ion Source at 60 Hz  0.5 ms pulse from the chopper, ~5 ms after the start of the IS pulse  ‘Ion Clearing’ on  Kicker plate biased to -300 V 24 hours without any trip 11 10 ms 0.5 ms Ion source extractor voltage Chopper voltage 0 kV -5 kV 5 ms -300 V DCCT (0.5 mA/div) Faraday cup (0.5 mA/div) IS pressure (1e-5 torr/div) Extraction voltage (0.05 kV/div) 24 hours Interruptions due to measurements with emittance scanner i.e. not trips

12. Beam parameters stability 12

13. Emittance constant to within ±2 % Beam current changed by 5.6% (min-max) over the entire run Alpha changed (min-max) by 35% and beta by 11% If any, possible correlation between beam size and current Beam parameters evolution during DC run 13 0.5 mA time Similar observations for pulsed beam run + large variations within pulse

14. Beam/machine stability/reproducibility Standard file (#1553) with settings close to ‘matched’  5 mA (DCCT), 1 ms pulse at 10 Hz Periodically record phase space  Significant spread  Linear behavior (  vs.  )  Could be explained by changes in neutralization  Similar behavior when changing beam current on purpose (i.e. ‘Study’) 14 ‘High’ current (5.2 mA) ‘Low’ current, (~4.5 mA) 1% cut, Slice 15 i.e. 0.375 ms into the pulse  , cm

15. Matching to RFQ 15

16. Optics Good model still needed to understand:  How to match the beam to the RFQ  Observed drifts of the Twiss parameters Simulations in progress  No consistent agreement between measurements and TRACK simulations yet  To help with interpretation of differential trajectory-like data, in- solenoid correctors have been implemented in TRACK by Jean- Paul Carneiro Do not have quantitative model of neutralization 16 Done semi-empirically so far

17. RFQ matching Without matching constraints:  Achieved 5 mA DC with  n,rms < 0.15 mm mrad Matched parameters (design):   = 7 cm and  = 1.6 at RFQ 1 st vane tip 17 32 mm For illustration only RFQ vane tip Emittance scanner front slit Solenoid #2 Solenoid #3

18. ‘Matched’ solution (I) Emittance larger than what has been measured before when not trying to reach certain Twiss parameters 18 AllisonScan-2014-09-16_11-45 5 mA, 0.4 ms pulse at 10 HZ, 2% cut, Slice 15 (i.e. 0.375 ms into the pulse)  = 0.65  = 86 cm  rms,n = 0.105 mm mrad AllisonScan-2014-12-17_09-13 5 mA, 1 ms pulse at 10 HZ, 2% cut, Slice 15 (i.e. 0.375 ms into the pulse)  = -6.04  = 72 cm  rms,n = 0.250 mm mrad B Sol1 = 141.4 A B Sol2 = 188.5 A B Sol3 = 210 A B Sol1 = 164.2 A B Sol2 = 275.5 A B Sol3 = 171.3 A X, mm X’, mrad Close to matched Twiss parametersArbitrary Twiss parameters × ~2.5

19. ‘Matched’ solution (II) Same beam line settings, different IS ‘tune’  Appears to be leading to lower emittance 19  = -4.84  = 53 cm  rms,n = 0.122 mm mrad AllisonScan-2014-12-17_09-13 5 mA, 1 ms pulse at 10 HZ, 2% cut, Slice 15 (i.e. 0.375 ms into the pulse)  = -6.04  = 72 cm  rms,n = 0.250 mm mrad B Sol1 = 141.4 A; B Sol2 = 188.5 A; B Sol3 = 210 A X, mm X’, mrad AllisonScan-2015-01-07_16-18 5 mA, 1 ms pulse at 10 HZ, 2% cut, Slice 15 (i.e. 0.375 ms into the pulse) Beam profiles 24 mm Caveat: Integrals not quite the same ÷ ~2

20. Readiness for RFQ Installation/Commissioning 20

21. Setup with mock-up interface flange 21 To test the scraper, a mock-up LEBT/RFQ interface flange is being built  While the ‘flange’ is not re-usable, the vacuum chamber attached to it can be used as an emergency spare Mock-up interface flange Scraper assembly T. Hamerla

22. Beam line status 22 Scraper and beam stop are the only remaining components required to be tested before RFQ commissioning (with beam) can take place  Scraper: RFQ vane protection (and on-line beam measurements)  Design complete  All drawings have been completed and parts are being fabricated  Procured long lead items  Delivery expected 1 st week of February ‘15  Installation expected mid-February ‘15  Beam stop: Personnel protection  Design to start next week

23. Movable isolated electrode with holes  Beam measurements and RFQ protection LEBT ‘scraper’ 23 LEBT/RFQ Interface flange Up/down motion with stepper motor Scraping edge Pencil beam aperture Regular aperture T. Hamerla

24. Outlook 24 On-track to be ready for RFQ arrival in the Spring  Nearly demonstrated all beam requirements for PIP-II RFQ Delivery

25. 25 Additional slides

26. Setup in picture 26 ‘Diagnostics’ box Chopper assembly Gate valve Emittance scanner (not visible)

27. Beam line picture 27 Gate valve ‘Diagnostics’ box Isolated diaphragm water hoses connectors Ion gauge Turbo pump DCCT Toroid Chopper assembly