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Accelerator Physics and Engineering

Josef FrischTonee Smith

Clive FieldAlan FisherHenrik Loos

Jeff RzepielaMark PetreeSteve SmithJim WelchGlen WhiteWalter WittmerMark WoodleyGerald Yocky

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APE – What do we do?Mission: Make accelerators work

Work in the intersection between physics, engineering and operations

Hardware design, construction and commissioning

High level software for beam modeling, diagnostics and controls

Machine operations and commissioning and experiments

Non-experts, non-specialists

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Types of Projects

Long-term projects:ATF2 tuning, THz source

Fast and simple:X-ray diagnostics, RF interlocks

Cutting-edge systems:10fs timing, Proton synchrotron light monitor

Simple brute-force: X-ray shutter, RF interlocks

Fast clean-up of systems that were delayed or non-functional: Get it working, make it pretty later.

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Involvement in Major Projects ATF2 - Linear Collider final focus test, Located at KEK – Japan

Modeling, Beam Position Monitors CTF3 - Test facility for a linear collider located at CERN

Beam Position monitors FACET - Plasma wakefield accelerator test at SLAC

Installation management, commissioning, diagnostics LCLS - Worlds first hard X-ray laser at SLAC

Modeling, High level controls, Diagnostics, THz source LHC - High energy proton collider located at CERN

Proton Synchrotron light monitor, Experiment timing.

APE works in collaboration with other groups – no APE-only projects

Will just present a few selected projects

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TCAV Bunch Length MeasurementTransverse cavity provides time dependent kick

Optics for 90 degree phase advance

Longitudinal transformed to transverse

Profile monitor

-1500 -1000 -500 0 500 1000 15001000

1500

2000

2500

3000

3500

4000

4500xarea = 0.46 0.00 Mctsxmean = 0.02 0.00 mmxrms = 159.7 0.00 m

yarea = 0.42 0.00 Mctsymean = -0.02 0.00 mmyrms = 50.5 0.00 m

Position (m)

Co

un

ts

()

-1 -0.5 0 0.5 10

5

10

15

20

25

30

35

40

45

TCAV:LI24:800:TC3:AACT (norm)

Bea

m S

ize

(

m)

TCAV bunch length on WIRE:LI28:744 15-Jun-2010 17:58:04 Super

y = 36.93 2.00 m

z = 2.5160.647 m

cal = 7.6850.347 m/m

LCLS uses a wire scanner to measure the profile

<10 fs bunch length measurement

TCAV + phase, - phase and off

TCAV on / off

15MV 2856MHz at LCLS

H. LoosH. Loos

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LCLS Short BunchesOperate with 20pC, near max compression, bunch length below TCAV resolution

Simulations (Genesis) indicate ~7fs FWHM bunch length (Yuantao Ding)

20pC, 160uJ, 9 KeV

Indirect bunch length measurement: FEL operates 1° L2 phase either side of full compression, but not at full compression (believed due to emittance growth)

0° phase 1°phase

No Lasing Good lasing

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Precision Timing LCLS produces few-femtosecond X-ray pulses Experiment laser produces ~40fs pulses

Commercial lasers available to ~20fs HHG can generate <1 fs XUV pulses.

Pump-probe experiments could use fs timing LCLS LINAC jitter (shot to shot relative to a

perfect clock) is ~60fs RMS Probably limited by high power RF system – very

expensive to improve Need to measure beam time and correlate with

experiments

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Beam arrival time cavity (LCLS)Similar to a cavity BPM but use the monopole mode

Phase drift from cavity temperature is the most significant problem

1us time constant, 10-5 /C° temperature coefficient -> 10ps/C° (!)

Raw Signal

Phase slope gives cavity temperature

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Beam Arrival Time System

Cavity system installed and used for all pump/probe experiment since the start of the LCLS experimental runs M. Petree

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Beam Arrival Time Cavity - NoiseCompare 2 independent cavity systems to estimate noise

Present system designed for 250pC, needs more gain to operate properly at low charge

20pC

RMS difference between cavities ~12 femtoseconds RMS at 250pC, ~25 femtoseconds at 20pCDrift is ~100 femtoseconds p-p over 1 day.

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Full Timing System

M. Petree, LBNL timing group. LCLS Laser group

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Timing System Performance 50fs RMS

From R. Coffee experiment. Pretty good, but need to eventually do much better

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Timing Upgrades

Phase Detector

Laser amplifier chain

Laser timing jitter believed to be the largest noise source in the system

Laser timing detection is one of the limits on system timing stability / noise. Photo-diode maximum signal limited by non-linear amplitude-to-phase conversion, Noise limits operation at low signal levels

Will test etalon system soon

Add an etalon to multiply the laser rate from 70MHz to 2856MHz

Low signal is OK, have more than we can use

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Future TimingElectronic timing likely not possible below ~10fs, need direct measurement of X-ray vs. Laser time in the experimental chamber

GaAs or similar

Laser

X-rays Reflected optical beam measured on array sensor

X-rays generate carriers that change the index of refraction and change the reflectivity near Brewsters angle

Suggested by a many people, not sure who originiated the idea.Initial tests at SXR

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“Slotted Foil” short bunches

6 m emittance

1 m emittance

“V” Foil position scan

No direct pulse length measurement

Slotted foil designed by P. Emma, installed by C. Field, M. Petree, D. Karach

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Low Charge AND Slotted Foil

X-ray spectrum with 20pc operation – few spikes suggest ~5 fs pulses

With 20pc and slotted foil see single spike spectrum suggests very short pulses

No direct measurement but may be producing ~1fs X-ray pulses

Various combinations of high / low charge and slotted foil used by multiple experiments during the 2010 LCLS experiment run

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THz Generation at LCLSUse short pulse (~70fs), high peak current (3000A), electron beam from the LCLS accelerator to generate THz to far IR broadband light for experiments.

Partially motivated by very large (106 Enhancement) of light from coherent transition radiation.

Real color COTR image

Use Transition Radiation from thin (2um) Be foil installed after the undulator.

Non-invasive for X-ray energies above ~ 1.5 KeV

Eventually will run 2 bunches:High charge, ultra-short (poor emittance ) for THz pumpLow charge FEL bunch for X-ray probe

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THz System

b o lo m e te r

P y r o d e t e c to r

Pyro cam.T H zA u t o -c o r r e l a t io n

S a m p le s t a g e/ p in h o le xy z s t a g e flip mirroriris

M o t o r i ze d fi l t e r s e t

Laser

Q W P

Z n T e

B S

E O s a m p l i ngB a la n c e d

D io d e s / A n d o r

T2 A

T ,2A

T

2A

3T

2A

R

R

T

A l ig n m e n tl a s e r

2A

D e la y s t ag e

2A

B S

2A

H a l f w a v e p la te R flip mirror e −

Simulation by H. LoosA. Fisher, A. Lindenberg (PULSE)

~3V/Å Electric FieldLab source: .01V/Å

Experiment laser800nm20fs pulses68 MHz, 150mW

Characterize THz, then use for experiments

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THz StatusOptics installed in tunnel, expect to test with beam soon

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X-ray Beam Diagnostic StationAfterthought in LCLS Design – constructed to replace the unfinished Front End Enclosure

Now used as a general purpose X-ray diagnostics chamber

Insert-able samples (15): materials tests, X-ray edge filters

YAG screen (upstream X-ray spot size monitor)

B4C MPS stopper to protect downstream PPS stoppers

BEAM

T. Smith, E, Kraft

First LCLS lasing seen with this system

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X-ray Diagnostic Station

Diagnostic station filter set

Thermal-acoustic sensor for calibrated X-ray measurements under development

X-rays → heat → acoustic wave → ultrasonic microphone

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LCLS Apps Optimization: Correlation plot -> Emittance ->

(profile monitor, or wire scanner app). Very powerful tool – for example can scan orbit

bump in the LINAC to minimize emittance Analysis: Undulator K measurement,

wakefields, , Bunch length, profiles, etc. Modeling: Matlab, XAL, etc.

Configuration in Mad / Oracle database

M. Woodley

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LCLS High Level AppsCorrelation plot

EmittanceApplication

Profile Monitor

Integrated set of applications for beam measurement and optimization

H. LoosJ. Rzepiela

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LCLS Apps (Sample only)

Matching, XAL or Matlab model

Emittance vs gun Solenoid

Transverse cavity bunch length measured with wire scanner vs phase

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X-ray Self Seeding at LCLS

Working in collaboration with photon science and ANL to make a self-seeding tests at LCLS at 1Å in spring of 2011

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LCLS_II

Calculations for wide range (200eV to 20 KeV) X-ray gas attenuator using variable apertures

Avoid speckle from Be attenuator. Investigating other materials

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J. Welch

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FACET

Lots of activity getting 2km of accelerator, 2 damping rings, a positron source and a new beamline ready. (W. Whittmer, J. Yocky)

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FACET

Fixed Foil

Pyro Detector

CCD Camera

Diamond Window

Si Beam Splitter

e-Beam

New Database, ModelM. Woodley

FACET bunch length monitors modified from LCLS designAlso used as OTR monitorH. Loos

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ATF2

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ATF2 Tuning / Controls

Main system used = VSYSTEM + SAD online model Mainstay for accelerator operations, tested, maintained and

stable. Alternate system developed based on EPICS+ Matlab + Lucretia

beam dynamics code: ATF2 “flight-simulator” Portable for offsite code development and testing Same software runs either in production or simulation mode

using simulation mode of low-level EPICS controls. Can interface to other code through tcp/ip socket layer or EPICS

DB interface.

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ATF2 Spot Size

Project goal is 30nm.Optimization of the non-linear final focus is very complex – needs sophisticated tuning tools.Spot size measurement is “Shintake” interference monitor, requires 10nm beam position measurement.

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ATF2 Cavity BPMs

ATF2 I/Q BPM system with 10nm RMS noise

Honda et. al.

LLNL cavity BPM support / mover system

Use 2 BPMS to predict measurement of 3rd

Prediction vs measured

20nm resolution15um range

50nm drif 1 hour

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Cavity BPM ElectronicsBPM signal6426 MHz

6.7 GHzLow Pass

Reject higher order modes

AmplifierImagerejectMixer

LO 6446 MHz

3 GHzLow pass

filter

Eliminate RF

20dBpre-

amplifier

Low Noise

20MHz

12dBamplifier

High IP3

40MHzlow pass

Anti-aliasfilter

100Ms/s14 bit digitizer

Low cost PC board construct for quantity production6dB noise figure, 70dB linearity measured27nm RMS noise at ATF2

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ATF2 Project Issues

Magnet Multipoles – may prevent operation below 250nm with re-measure and shim.

Need 10nm BPMs to demonstrate 30nm IPspot size. Possible but this equals the best performance ever seen with BPMs

ATF2 second goal of 1nm position stability would require 800 picometer cavity BPMS; Happy to try – but very unlikely to be able to reach

this resolution!

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CTF3

BPM Signal RF Signals

Facility at CERN to test 2-beam acceleration for the CLIC collider

APE (S. Smith) working on drive beam BPMs. this is considerably more difficult than it sounds! The drive beam is designed to produce 100s of MW in a power extraction structure – it couples an unmanagable amount of power into any BPM pickup.

One option: use an off-frequency narrow-band BPM and the statistical fluctuations on the drive beam.

power extraction structure

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LHC – Synchrotron Light Monitor Two applications: BSRT: Imaging telescope, for transverse beam profiles BSRA: Abort-gap monitor, to verify that the gap is empty Particles passing through the abort kickers during their rise get

a partial kick and might quench a superconducting magnet. Two particle types: Protons and lead ions Three light sources: Undulator radiation at injection (0.45 to 1.2 TeV) Dipole edge radiation at intermediate energy (1.2 to 3 TeV) Central dipole radiation at collision energy (3 to 7 TeV) Spectrum and focus change during ramp

A. Fisher

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LHC

To R F cav itie s an d I P 4To a rc

Cry os ta t

E xtrac ted lig h t s en t to an op tica l tab le

b e low th e b eam lin e

1 .6 m rad

7 0 m

2 6 m 9 3 7 m m

5 6 0 m m

4 2 0 m m

D 3 U

1 0 mD 4

1 9 4 m m

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LHC Synchrotron LIght monitor Works!

H o rizo n ta l0 .6 8 m m 0 .7 0 m m

Vert ica l0 .5 6 m m 1 .0 5 m m

L ig h t fro m D3 d ip o le.B lu e fi l te r. Na rro w sli t.

This Fall: Synchtrotron light images from....LEAD!

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Other Stuff

Dark matter "Heavy Photon" search at Jeffreson lab Design / tests for thin high average power W target.

(C. Field) Timing system for forward proton detector at

LHC 1ps timing over 500M in high radiation environment.

NLCTA: Obvious place for APE to work, but so far too manpower limited

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Future

Expect to continue with a random collection of projects using a wide variety of technologies

APE wouldn't be needed in a perfect lab – but has been valuable in a real one.