Novel Beam Diagnostics on PXIE Vic Scarpine, FNAL 2nd Annual PASI Meeting April 3-5, 2013.

Novel Beam Diagnostics on PXIE

Vic Scarpine, FNAL

2nd Annual PASI MeetingApril 3-5, 2013

2

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

2013 PASI Meeting, Vic Scarpine


Project X Injector Experiment: PXIE

• 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

RFQ MEBT HWR-CM SSR1-CMH- LEBT

~ 40 m long

HEBT/Dump

1 mA~ 25 MeV

5 mA~ 2.1 MeV

5 mA30 keV

1 mA~ 2.1 MeV

4

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 detectionList of ~ 15 unique instruments needed for PXIE

5

Source-LEBT Instrumentation

Beam Current– Unchopped Beam Current

• DCCT– Chopped Beam Current

• Toroid pickup

Beam Emittance– Water-cooled Allison Scanner

• Measurement at ion source• Collaboration with SNS


Allison Emittance Scanner

LEBT

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MEBT Instrumentation

MEBT Operational Beam Measurements: (red = CW)

• Transverse position - BPMs

• Bunch Phase – BPMs time-of-flight beam energy

• Beam Current – DCCT, Toroids, RWCM (resistive wall current monitor)

• Extinction – RWCM with fast scope

• Transverse shape – wire scanners, laser wires

• Transverse emittance – slit/multiwire (low-res), double slit/Faraday cup (hi-res), Quad scans

• Longitudinal shape – laser wires, chopper, wire bunch shape monitor

• Absorber Profiler – OTR Imager or IR imager


RF Kick1 DumpRF Kick2 RF

Current HEBT concept

Multi-port Diagnostics

Box

Extinction Monitor

Quad doubletWith X&Y corr.

BPM (4 button warm)

High-PowerDump

RW

CM Sweeping dipole

H0 Profile Monitor*

H0

H-

Thin foil Absorber

Laser wire/Wire

Scannercombo

Laser wire/WireScannercombo

RWCM

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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

MEBT design

*H0 profile monitor: neutralization monitor emittance measurement

H+Dump dipole


From Dave Johnson’s talk

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

“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

2013 PASI Meeting, Vic Scarpine 9

MEBT/HEBT Quadrupole Block

Four button Warm BPM

HWR/SSR1Cold BPM

Requirements:Transverse resolution

• 0.03 mm (for a single ~1 μs macro-pulse) • 0.01 mm (CW)

Phase resolution - 0.1 deg (> 10 ms pulses)Bunch-by-bunch measurements in MEBT chopper regionSynchronize signal detection

• Allows for lock-in detection for laser wireMechanical 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

ChoppedBeam

Patterns

10

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


11

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

12

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

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


Preliminary SNS Measurements (Y. Liu)

Horizontal

Vertical

14

Vibrating Wire Halo Monitor

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


-4200 -4000 -3800 -3600 -3400 -3200 -3000 -2800 -2600 -24003600

3400

3200

3000

2800

2600

2400

2200

Fre

qu

en

cy o

f vi

bra

ting

wir

e (

Hz)

Position of vibrating wire (counts) Note: Frequency change is very sensitive to ambient temperature,

mechanical vibration, and magnetic field

Preliminary measurements made at HINS

Beampipe

Sensitive wire heated by beam

Beam

Moses Chung, FNAL

9.0 9.5 10.0 10.5 11.010-3

10-2

10-1

100

101

102

103

Vibrating wireF

requ

ency

cha

nge

(Hz)

Horizontal position (mm)

Vibrating wire may have much higher

dynamic range in the halo region

Preliminary Estimates of Instrument by Location

2013 PASI Meeting, Vic Scarpine 15

Current Position/Phase - BPM

Trans. Profiles

Trans. Emittance

Long. Profiles

Halo Beam Loss+

Extinction

LEBT 2 ---- ---- 1 ---- ---- ---- ----

MEBT 2 9 4 1 1* 1 TBD 1

HWR & SSR1

---- 12 1* (between CMs)

__ 1* (between CMs)

__ TBD __

HEBT 2 5 2* 1 + 1* 1 1 TBD 1

FE = focusing elementCM = cryomodule

* = laserwire+ = charged/neutral

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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


Novel Beam Diagnostics on PXIE Vic Scarpine, FNAL 2nd Annual PASI Meeting April 3-5, 2013.

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Transcript of Novel Beam Diagnostics on PXIE Vic Scarpine, FNAL 2nd Annual PASI Meeting April 3-5, 2013.