Novel Beam Diagnostics on PXIE

Vic Scarpine, FNAL 2nd Annual PASI Meeting April 3-5, 2013

Scope of PXIE*

Build an integrated systems test of the first ~ 30 MeV of Project X – Validate front-end concept to minimize technical risk elements – Demonstrate wideband chopper – Low b superconducting acceleration Integrated systems test goals: – 1 mA average current with 80% chopping of beam in MEBT – Efficient acceleration with minimal emittance dilution

The scope of beam diagnostics are to identify and provide the instrumentation systems necessary to successful commission, characterize and operate PXIE and to validate the system test goals.

* See Steve Holmes talk later in this session

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Project X Injector Experiment: PXIE

H LEBT RFQ MEBT HWR-CM SSR1-CM HEBT/ Dump • • • • • • • 5 mA 30 keV 5 mA ~ 2.1 MeV 1 mA ~ 2.1 MeV ~ 40 m long 1 mA ~ 25 MeV CW H- source delivering 5 mA at 30 keV LEBT with beam pre-chopping CW RFQ operating at 162.5 MHz and delivering 5 mA at 2.1 MeV

MEBT with integrated wide-band chopper and beam absorbers capable of generating arbitrary bunch patterns at 162.5 MHz, and disposing of 4 mA average beam current

Low beta superconducting cryomodules: 1 mA to ~25 MeV Beam dump capable of accommodating 2 mA at 25 MeV (50 kW) for extended periods.

Associated beam diagnostics

, utilities and shielding 2013 PASI Meeting, Vic Scarpine Page 3

PXIE Measurement Goals

• • • • Beam current – DCCTs, Toroids, High Bandwidth Resistive Wall Current Monitors (RWCM) Beam position and phase – Warm and cold BPMs Beam energy and energy spread – Time-of-flight from BPM phase, spectrometer magnet Beam transverse profiles – Wire scanners, multi-wires, laser wires • • • • • Beam transverse emittance – Allison scanner, slit-wire scanners

,

laser emittance monitor Beam longitudinal profiles – Wire-based bunch shape monitor, picosecond laser wires Beam halo – Vibrating wire, high-gain wires, laser wire, apertures, diamond detectors Beam loss monitoring – Ion chambers, neutron detectors Chopped beam extinction efficiency – High-Bandwidth RWCM, single (few) particle detection

List of ~ 15 unique instruments needed for PXIE

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LEBT

Source-LEBT Instrumentation

Allison Emittance Scanner Beam Current – Unchopped Beam Current • DCCT – Chopped Beam Current • Toroid pickup Beam Emittance – Water-cooled Allison Scanner • Measurement at ion source • Collaboration with SNS 2013 PASI Meeting, Vic Scarpine 5

MEBT Instrumentation

RF Kick1 RF Kick2 Dump RF • • • • • • • • MEBT Operational Beam Measurements: Transverse position BPMs Bunch Phase – Beam Current – Extinction – BPMs  time-of-flight  DCCT, Toroids, RWCM (resistive wall current monitor) RWCM with fast scope Transverse shape – wire scanners, laser wires Transverse emittance Longitudinal shape – Absorber Profiler – (red = CW) beam energy – slit/multiwire (low-res), double slit/Faraday cup (hi-res), Quad scans laser wires, chopper, wire bunch shape monitor OTR Imager or IR imager 2013 PASI Meeting, Vic Scarpine 6

Current HEBT concept

R W C M Extinction Monitor BPM (4 button warm) Multi-port Diagnostics Box Quad doublet With X&Y corr.

MEBT design Laser wire /Wire Scanner combo *H0 profile monitor: neutralization monitor emittance measurement

From Dave Johnson’s talk

Dump dipole H 0 H Thin foil H + H0 Profile Monitor* A b s o r b e r Sweeping dipole Multi-port diagnostics Box: (similar to • • • • • • SNS MEBT 6-pack) Extinction monitor -

tbd

Transverse emittance - slit/detector wire scanner and/or laser wire (if needed) halo monitor –

tbd

Longitudinal bunch shape monitor

future “unknown” diagnostics

Transverse Beam Position and Longitudinal Phase - Warm BPMs • Same as MEBT BPM design and functionality Beam Current Monitor • Two RWCM – like MEBT Profiles in dump line to measure energy spread 2013 PASI Meeting, Vic Scarpine 7

“Novel” Beam Diagnostic Issues and Instruments

nov·el

1

(nvl)

n.

1. A fictional prose narrative of considerable length, typically having a plot 2. Strikingly new, unusual, or different.

Warm and Cold BPMs

Requirements:

Transverse resolution

•

0.03 mm (for a single ~1 μs macro-pulse)

•

0.01 mm (CW) Phase resolution - 0.1 deg (> 10

m

s pulses)

Bunch-by-bunch measurements in MEBT chopper region

Synchronize signal detection

• Allows for lock-in detection for laser wire Mechanical Issues: • Warm BPMs embedded in Quads • Cold BPM stability in CM Signal Processing Issues: • Arbitrary beam pattern from MEBT chopper • Multiple paths through MEBT chopper Chopped Beam Patterns HWR/SSR1 Cold BPM 2013 PASI Meeting, Vic Scarpine MEBT/HEBT Quadrupole Block Four button Warm BPM 9

MEBT Chopper Extinction Measurement

• Use upstream and downstream Resistive Wall Current Monitors (RWCM) Extinction > ‘SBD-like’ monitor – Average over many bunches – < 1 Hz BW – Fits to bunch shape – Measure impact on adjacent bunches 2013 PASI Meeting, Vic Scarpine 10

Combined Wire Scanner Laser Wire Unit

• • • • • Transverse 3-wire wire scanner plus laser wire module Hybrid wire scanner with laser ports – Modified version of SNS design Wire scanner in pulsed beam operation only Laser wire in either pulsed or CW beam operation Laser wire intended to measure transverse and longitudinal profiles –

Will different lasers be required for transverse versus longitudinal measurements?

Can wires or lasers measure profile tails/halo?

– Transverse halo measurements with wire suffer from cross-talk – Halo measurement with laser suffer from scattered light effects

Locations: MEBT, between SC cryomodules, HEBT

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Low-Power Transverse and Longitudinal Laser Wire

• • •

Mode-locked psec laser used to measure both transverse and longitudinal profiles

Laser rep-rate is locked to accelerator RF Distribute modulated laser pulses via fibers • Narrow-band lock-in amp detects modulated signal Measure profiles by either: • Collection of electrons • Use BPM as notched-beam pickup would allow laser monitor to fit between cryomodules • • • • Questions: What is the photodissociation efficiency?

What are the noise issues?

What are the nonlinear limits to power in the fiber?

What signal-to-noise ratios and averaging times are practical?

Fall back laser wire option is to use high-power laser technique similar to SNS R. Wilcox, LBNL

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Laser Wire Emittance Monitor

Preliminary SNS Measurements (Y. Liu) Horizontal Laser Wire Emittance Monitor – Laser acts like slit  x • Generates H0 – H0 profiler measure H0 divergence  x’ • Background from beam neutralization – Demonstrated at SNS

Operate at the end HEBT

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Vibrating Wire Halo Monitor

Beampipe Beam Temperature change affects the tension of sensitive wire and results in the shift of resonance frequency of the vibrating wire in permanent dipole magnets.

2200 2400 2600 2800 Preliminary measurements made at HINS 3000 Sensitive wire heated by beam 3200 3400

Moses Chung, FNAL

10 3 3600 -4200 -4000 -3800 -3600 -3400 -3200 -3000 -2800 -2600 -2400 Position of vibrating wire (counts) Vibrating wire 10 2 10 1 10 0

Note: Frequency change is very sensitive to ambient temperature, mechanical vibration, and magnetic field

10 -1 10 -2 10 -3 9.0

9.5

10.0

10.5

Horizontal position (mm) 11.0

Vibrating wire may have much higher dynamic range in the halo region

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Preliminary Estimates of Instrument by Location

LEBT MEBT HWR & SSR1 HEBT

Current

2

Position/ Phase - BPM

--- 2 9

Trans. Profiles

--- 4

Trans. Emittance

1 1

Long. Profiles

--- 1*

Halo

--- 1

Beam Loss +

--- TBD

Extinction

--- 1 --- 2 12 5 1* (between CMs) 2* __ 1 + 1* 1* (between CMs) 1 __ 1 TBD TBD __ 1 FE = focusing element CM = cryomodule * = laserwire + = charged/neutral 2013 PASI Meeting, Vic Scarpine 15

Technical Challenges

• • • Many PXIE beam diagnostic instruments are based on previous designs – Most are low technical risk – Medium risk items • MEBT chopper BPM measurements • MEBT extinction measurement • Wire scanner – laser wire combination unit • Low-energy Beam Loss Monitoring – Higher risk items • Low-power laser wire • Laser transverse emittance monitor • Vibrating wire halo measurements and transverse and longitudinal tails/halos in general Largest risks involve either laser-based measurements or halo measurements

Collaboration with other groups important for diagnostics success

–

PASI Postdoc, Richard D’Arcy, to help with these problems

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