PXIE Beam Diagnostics First Thoughts Manfred Wendt Fermilab
PXIE Beam Diagnostics ‒ First Thoughts ‒ Manfred Wendt Fermilab
Outline • • Overview LEBT & MEBT Beam Diagnostics – including some examples • • • A few remarks to BPMs To Do List Backup – Helical chopper EM analysis April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 2
Laundry List • Characterization of the beam parameters – – – – – • Beam current: DCCT, toroid, RWCM Beam orbit: button-style BPMs, digital read-out electronics Beam losses: BLMs(? ) Beam energy & phase: BPMs, TOF & spectrometer in diagn. BL Beam emittance: Allison scanner, slit & wirescanner, laser-wire Long. Profile: mode-locked laser, Feschenko-wire, fast F-cup Bucket extinction monitor: 3 D-SEM, RWCM, ? Transverse halo: vibrating wire, collimators Longitudinal tails: 3 D-SEM, Feschenko-wire Will not cover everything – Some examples, open questions, preliminary ideas… April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 3
LEBT Diagnostics H- Source Emittance Station RFQ Not for PXIE Beam Current Monitor (DCCT) • Which LEBT layout? – Does the DCCT needs to detect chopped beam? – Digital DCCT with toroid bandwidth extension? ! • No BPMs? – How do we insure a lowloss beam trajectory between source and RFQ? • Allison scanner for beam emittance characterization – Need for a water-cooled device? ! – Collaboration with SNS? ! April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 4
PXIE DCCTs • Based on NOv. A/ANU design – DC… 400 Hz BW DC-CT – 400 Hz…~1 MHz AC-CT • Shielding of external fields – Minimize real-estate (length)! – Need to understand shielding requirements! April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 5
MEBT Diagnostics • Beam emittance – Slit & wire based – Photo-detachment (laser wire) • Extinction monitor – Low-cost resistive wall-current monitor (RWCM) – 3 D SEM system • Longitudinal profile – Fast Faraday cup (invasive) April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 6
MEBT Emittance • 3 instruments – Slit & multiwire – 3 -wire-scanner (hor. , vert. , diag. ) – Laserwire (transv. & long. ) • Single unit wire & laser-Scanner Option 1 – SNS design • Option 1 Option 2 – Fermilab-style emittance probe • Option 2 – Separate slit & multiwire (dither option, compact) April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 7
Hor. Phase Space along Pulse (HINS) • X – X’ along beam pulse; arbitrary units • 6 m. A beam April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 8
HINS Beam Emittance Thick Quad Scan Analysis. TRACK simulations with different Input Emittances. April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 9
Laser Wire for H- Beams e- F-Cup Galvanometer E or B H- H- +γ H- + Laser beam • • H- Beam H 0 Laser Beam H- neutralization by photo-detachment – Cross-section σmax ≈ 4. 2 x 10 -17 cm 2 – Electron binding E 0 = 0. 7543 e. V Typical HINS / PX MEBT parameters – Ebeam = 2. 5 Me. V, Nd: YAG laser 1064 nm, 900 angle, -> σ ≈ 3. 66 x 10 -17 cm 2 – Requires laser energy ~ 10 -30 m. J April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 10
Laserwire (transverse & long. ) • Mode-locked psec laser for transverse and longitudinal beam profiles – LBNL analysis proposes low-power fiber laser source – NB lock-in amp detects modulated signal – Detect detached electrons Ø Deflect into Faraday cup Ø Use BPM as notched beam pickup at cryomodule locations. • Many open questions: – – Photo-dissociation efficiency? S/N issues!? Non-linear effects in the fiber? BPM as sensitive current detector? April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 11
Extinction & Current Monitor • Single bunch RWCM – BW: 10 k. Hz – 4 GHz • • Average single bunch measurements (“SBD-like”) Successful design for EMMA – Build 4 units, each ~$10 k • Use as beam current monitor April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 12
Time-resolved SEM (M. Hori) • 3 D SEM – – 2 mm spatial resolution <1 nsec time resolution 108 dynamic range np = 10 protons / pulse sensitivity April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 13
Longitudinal Bunch Shape – Fast Faraday Cup (SNS) ~ 12 GHz bandwidth • Some limitations by signal cable Preliminary April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 14
Longitudinal Shape VS RFQ Power 300 KW Feed fast Faraday Cup into high bandwidth scope (6 GHz ABW) to measure bunch shape. 240 KW 220 KW 200 KW April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 15
“Button” BPM Pickup Analysis April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 16
Button BPM Geometry • Different button-BPM style options – Welded, flange-mount – Commercial, home-brew • Issues: – – Longitudinal space, mounting Cleanliness, UHV RF properties Tolerances April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 17
BPM Read-out Electronics • Based on Direct Digital Down-Conversion (DDC) – 12 ch, 250 MSPS ADCs, 900 MHz BW, VME/VXS – Simultaneously measure 1 st & 2 nd beam harmonics – Beam position & phase (TOF) April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 18
Position Resolution (PIP Electronics) • SVD with only 6 position measurements (3 H, 3 V) – Ideally expect up to 3 modes to correlate with initial trajectory & energy – With only 6 pickups, real noise sneaks into modes • Conservative estimate resolution < 40 um April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 19
Phase Resolution (PIP Electronics) • • Measured on 2 nd Harmonic at 402 Mhz Expect correlations from Beam & LO – SVD suffers from only 3 pickups… • Estimate resolution < 0. 1 degree at 402 MHz April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 20
To Do List • Function Requirements for PXIE Beam Diagnostics – – Beam parameters – nominal, minimum, maximum Operating conditions, beam commissioning Agree on beam-line layout and components Available real estate for beam diagnostics Ø Long. space, flange styles, beam pipe apertures, etc. – UHV, cryo and cleanroom requirements Ø Materials, fabrication and assembly procedures, clean-ability – Read-out & control electronics Ø Location of racks, cabling, DAQ, infrastructure • Prototyping & beam tests – HINS, PIP, beam studies outside Fermilab? ! • Focus on LEBT beam diagnostics – DCCT, Allison scanner, LEBT BPMs? April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 21
Thank You! April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 22
Broadband Chopper 134. 3 mm vbeam = 20. 0 mm/nsec v. E-field = 20. 00 mm/nsec ~26 mm (6σ) • Broadband chopper, Ebeam = 2. 1 Me. V: – Travelling wave structure v. E-field = vbeam – High Etr-field, ideal: 3. 0 nsec rectangular pulse Ø More realistic: trapezoidal pulse, 2 nsec rise – 2 nsec flat top – 2 nsec fall Etr ℓki – Kick angle = ≈ 2 E 0 γ β 5 MV – For 7. 5 mrad deflection and 500 mm effective length: Etr ≈ 75 k. V/m – Basically only the E-field is used for the beam kick April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 23
Helical Electrode, ~50 cm • 55 turns, with “electrodes” – Greg’s prototype dimensions • • x = - 8 mm from mirror plane Surrounding ground box Output port (#2) April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 24
Port Signals April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 25
E-Fields on Beam Axis • Need to check the normalization! April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 26
E-Field at 16 nsec (y = 0 mm) April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 27
E-Field at 29 ns (z = 447 mm) April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 28
Impedance Analysis • Work in progress – Use 5. 5 turns – Play with dimensions and distance of the vacuum housing. April 11, 2012 – PXIE Beam Diagnostics (M. Wendt) – Project X Collaboration Meeting, LBNL, April 2012 Page 29
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