Design optimisation of a scraper and Ionisation Monitor

Design & optimisation of a scraper and Ionisation Monitor for Beam Profile Measurement on ELENA BI Day 2017. 06. 29 Pierre Grandemange On behalf of experimental areas section

Overview • • ELENA – Extra Low Energy Antiproton ring Scraper : antiproton beam profile monitor Scraper : H-/proton beam profile monitor IPM - Ionisation Profile Monitor 9/24/2020 BI Day – Pierre Grandemange 3

ELENA Extra Low Energy Antiproton ring 9/24/2020 BI Day – Pierre Grandemange 4

PS Target AD ELENA Goal Range 9/24/2020 25 Ge. V protons pbar @ 2. 7 Ge. V -> 5. 3 Me. V -> 100 ke. V Cold Antihydrogen 25 Ge. V -> ~1 me. V BI Day – Pierre Grandemange 5

ELENA properties ELENA length 30 m Mean pressure 4. e-12 mbar Antiprotons – pbar - beams • ~ 2. e 7 pbar/beam • Injection energy 5. 3 Me. V • Extraction energy 100 ke. V • Full cycle 25 -30 seconds H-/protons beam (commissioning) • 100 ke. V Energy (Me. V) 5. 3 0. 653 0. 100 9/24/2020 BI Day – Pierre Grandemange 6

scraper Free space: IPM ? ! November the 24 th, 2016 9/24/2020 BI Day – Pierre Grandemange 7

SCRAPER antiprotons (pbar) beam profile monitor H- ions / protons beam profile monitor 9/24/2020 BI Day – Pierre Grandemange 8

Scraper : the device beam 9/24/2020 BI Day – Pierre Grandemange 9

working principle - pbar Scintillating detector N secondary pions scraper beam time (~1 s) Vacuum chamber 9/24/2020 BI Day – Pierre Grandemange 10

Geant 4 simulation - pbar • Two scintillators • More signal than in the AD: less scattering at low energies • Scintillators size, orientation and position 9/24/2020 BI Day – Pierre Grandemange 11

working principle - H-/proton Scintillating detector No annihilation Ø no pions Ø no signal in scintillators secondary pions scraper H- / proton beam Vacuum chamber 9/24/2020 BI Day – Pierre Grandemange 12

working principle - H-/proton No annihilation Ø no pions Ø no signal in scintillators detector in vacuum (4. e-12 mbar) secondary electrons scraper H- / proton beam detect secondary electrons Ø are there any? Ø how many? Ø where? Vacuum chamber 9/24/2020 BI Day – Pierre Grandemange 13

Geant 4 simulation - H-/proton • Anisotropic emission • scraper geometry: a bevel improve secondary emission Ø Choice of 4 MCP detectors MCP = Micro Channel Plate 9/24/2020 BI Day – Pierre Grandemange 14

The ELENA scraper is equipped with two acquisition systems • The secondary electron emission detection system should work with protons/H-/antiprotons • • Commissioning is ongoing 9/24/2020 BI Day – Pierre Grandemange 15

IPM Ionisation Profile Monitor 9/24/2020 BI Day – Pierre Grandemange 16

ELENA properties The IPM - Ionisation Profile Monitor - will satisfy all your wishes! • AD extraction : 110 seconds • Profile measurements with the scraper at different cycle step is very long/tedious Ø Difficult to observe electron cooling efficiency in the transverse plane 9/24/2020 BI Day – Pierre Grandemange 17

IPM principle Spatial sensitive detector (MCP + anode tubes) V- Top electrode +- - + +- -+ -+ -+ Residual gas -+ +Beam V+ Bottom electrode 9/24/2020 BI Day – Pierre Grandemange 18

Ionisation rate in ELENA antiproton flux gas density H 2 @ 3. 8 e-12 mbar gas ionisation cross section with antiprotons @ 100 ke. V linear ionisation rate @ 100 ke. V Ø 4. 6 ions /1 cm/100 ms 9/24/2020 BI Day – Pierre Grandemange 19

9/24/2020 cooling 2 deceleration 2 cooling 1 deceleration 1 Ionisation in ELENA Ø Cheat a little by injecting gas? ! BI Day – Pierre Grandemange 20

Gas injection impact Ø ionisation from IPAC 2014, TUPRI 028, C. Carli Ø large angle scattering loss Ø emittance blow up 9/24/2020 BI Day – Pierre Grandemange 21

Pressure constraint large angle scattering loss criterion: “loss due to gas injection is less than 1. e-4 the normal loss over a full cycle” Ø point emittance blow up criterion: “emittance blow up growth due to gas injection should not exceed 5% of emittance decrease during electron cooling” Ø point 9/24/2020 BI Day – Pierre Grandemange 22

9/24/2020 cooling 2 deceleration 2 cooling 1 deceleration 1 Ionisation in ELENA Ø Cheat a little by injecting gas? ! BI Day – Pierre Grandemange 23

Ionisation in ELENA CO 2 @ 1. 0 e-11 mbar 9/24/2020 Ø 9% average pressure rise BI Day – Pierre Grandemange 24

IPM design Design based on AD and LEIR IPM • Double MCP • Read-out : stainless steel tubes • XHV material compatible only External dimensions: 206 x 140 x 128 mm Beam aperture: 82 x 70 mm 9/24/2020 Two orbit correction electrodes Long detection length : 80 mm BI Day – Pierre Grandemange 25

integration in ELENA Bellow Gas injection Horizontal BIPM + NEXTorr D 1000 -10 Turbo-molecular pump 9/24/2020 Bellow Vertical BIPM + NEXTorr D 1000 -10 Document reference 26

Conclusion • • The scraper’s detection systems are installed and ready. ELENA Commissioning with H- (and pbar) has started, profile measurement soon! We propose to install an IPM in ELENA, especially to monitor electron cooling efficiency: preliminary study is promising. A engineer change request is available on EDMS: https: //edms. cern. ch/document/1754985/0. 1 9/24/2020 BI Day – Pierre Grandemange 27

3 7 4 2 6 5 4 List of equipment for BI in ELENA 1. BPM (20) 2. Pick up Shottky longitudinal 3. BTVs 4. Tune “BBQ” 5. Electron Cooler 6. Scraper 7. Empty space ? !

Geant 4 • pbar -> pions • plastic scintillator • Polyvinyltoluene (EJ-2125) 255 mm • 50 mm (radius)*2 mm • 10000 photons/Me. V (e-) • rise/decay time : 0. 9/2. 4 ns 70 mm 200 mm 9/24/2020 BI Day – Pierre Grandemange 31

pbar results – energy deposition 9/24/2020 BI Day – Pierre Grandemange 32

9/24/2020 BI Day – Pierre Grandemange 33

Scraper bevel

Scraper bevel

Scraper - see 9/24/2020 BI Day – Pierre Grandemange 36

IPM - molecules cross sections 9/24/2020 BI Day – Pierre Grandemange 37

IPM - gas 9/24/2020 BI Day – Pierre Grandemange 38

IPM - vacuum chamber 9/24/2020 BI Day – Pierre Grandemange 39

IPM – comsol simulation 9/24/2020 BI Day – Pierre Grandemange 40

IPM – comsol simulation 9/24/2020 BI Day – Pierre Grandemange 41