ccelerator hysics and ngineering Josef Frisch Tonee Smith

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1 A ccelerator P hysics and E ngineering Josef Frisch Tonee Smith Clive Field Alan Fisher Henrik Loos Jeff Rzepiela Mark Petree Steve Smith Jim Welch Glen White Walter Wittmer Mark Woodley Gerald Yocky 1

2 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 2

3 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. 3

4 Involvement in Major Projects ATF2 - Linear Collider final focus test, Located at KEK Japan CTF3 - Test facility for a linear collider located at CERN Installation management, commissioning, diagnostics LCLS - Worlds first hard X-ray laser at SLAC Beam Position monitors FACET - Plasma wakefield accelerator test at SLAC Modeling, Beam Position Monitors 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 4

5 TCAV Bunch Length Measurement Transverse cavity provides time dependent kick Optics for 90 degree phase advance Profile monitor Longitudinal transformed to transverse LCLS uses a wire scanner to measure the profile 15MV 2856MHz at LCLS 4500 T C A V b u n c h l e n g t h o n W IR E : L I2 8 : J u n : 5 8 : 0 4 S u p e r y a re a = ± M c ts y m e a n = ± m m y rm s = ± µm 45 TCAV on / off B e a m S i z e (µ m ) C o u n ts () x a re a = ± M c ts x m e a n = ± m m 4000 x rm s = ± µm σ y = ± µm σ z = ± µm 35 c a l = ± µm /µm <10 fs bunch length measurement TCAV + phase, - phase and off H. Loos P o s itio n ( µ m ) H. Loos T C A V : L I2 4 : : T C 3 : A A C T ( n o r m ) 1 5

6 LCLS Short Bunches Operate with 20pC, near max compression, bunch length below TCAV resolution 0 phase No Lasing 20pC, 160uJ, 9 KeV 1 phase Good lasing Simulations (Genesis) indicate ~7fs FWHM bunch length (Yuantao Ding) Indirect bunch length measurement: FEL operates 1 L2 phase either side of full compression, but not at full compression (believed due to emittance growth) 6

7 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 7 experiments

8 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 8

9 Beam Arrival Time System Cavity system installed and used for all pump/probe experiment since the start of the LCLS experimental runs M. Petree 9

10 Beam Arrival Time Cavity - Noise Compare 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 20pC Drift is ~100 femtoseconds p-p over 1 day. 10

11 Full Timing System 11 M. Petree, LBNL timing group. LCLS Laser group

12 Timing System Performance 50fs RMS From R. Coffee experiment. Pretty good, but need to eventually do much better 12

13 Timing Upgrades 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-tophase conversion, Noise limits operation at low signal levels Will test etalon system soon Phase Detector Laser amplifier chain Add an etalon to multiply the laser rate from 70MHz to 2856MHz Low signal is OK, have more than we can use 13

14 Future Timing Electronic timing likely not possible below ~10fs, need direct measurement of X-ray vs. Laser time in the experimental chamber X-rays Reflected optical beam measured on array sensor Laser GaAs or similar 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 14

15 Slotted Foil short bunches 6 µm emittance 1 µm emittance V Foil position scan No direct pulse length measurement 15 Slotted foil designed by P. Emma, installed by C. Field, M. Petree, D. Karach

16 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 16

17 THz Generation at LCLS Use 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. Use Transition Radiation from thin (2um) Be foil installed after the undulator. Non-invasive for X-ray energies above ~ 1.5 KeV Real color COTR image Eventually will run 2 bunches: High charge, ultra-short (poor emittance ) for THz pump Low charge FEL bunch for X-ray probe 17

18 THz System Delay stage T ~3V/Å Electric Field Lab source:.01v/å Laser BS e Sample s tage /pinhole xyz s tage 2A bolometer Half wave plate ZnTe EO sampling ro m flip R R Balanced Diodes/Andor BS QWP 2A. m ca yro P THz Autocorrelation ro m flip Experiment laser 800nm 20fs pulses 68 MHz, 150mW 2A R 3T 2A irs T,2A Characterize THz, then use for experiments 2A Pyro detector T T 2A Motorized filter s et Alignment laser Simulation by H. Loos 18 A. Fisher, A. Lindenberg (PULSE)

19 THz Status Optics installed in tunnel, expect to test with beam soon 19

20 X-ray Beam Diagnostic Station Afterthought in LCLS Design constructed to replace the unfinished Front End Enclosure Now used as a general purpose X-ray diagnostics chamber First LCLS lasing seen with this system 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 BEAM20 T. Smith, E, Kraft

21 X-ray Diagnostic Station Thermal-acoustic sensor for calibrated X-ray measurements under development Diagnostic station filter set X-rays heat acoustic wave ultrasonic microphone 21

22 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 22 M. Woodley

23 LCLS High Level Apps Correlation plot Profile Monitor Emittance Application Integrated set of applications for beam measurement and optimization H. Loos J. Rzepiela 23

24 LCLS Apps (Sample only) Matching, XAL or Matlab model Emittance vs gun Solenoid Transverse cavity bunch length measured with wire scanner vs phase 24

25 X-ray Self Seeding at LCLS Working in collaboration with photon science and ANL to make a selfseeding tests at LCLS at 1Å in spring of

26 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 26

27 27 J. Welch

28 FACET Lots of activity getting 2km of accelerator, 2 damping rings, a positron source and a new beamline ready. (W. Whittmer, J. Yocky) 28

29 FACET New Database, Model M. Woodley e-beam Fixed Foil Diamond Window CCD Camera Pyro Detector Si Beam Splitter FACET bunch length monitors modified from LCLS design Also used as OTR monitor 29 H. Loos

30 30

31 ATF2 31

32 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. 32

33 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, 33 requires 10nm beam position measurement.

34 ATF2 Cavity BPMs Prediction vs measured Use 2 BPMS to predict measurement of 3rd 20nm resolution 15um range LLNL cavity BPM support / mover system Honda et. al. 50nm drif 1 hour ATF2 I/Q BPM system with 10nm RMS noise 34

35 Cavity BPM Electronics BPM signal 6426 MHz 6.7 GHz Low Pass Reject higher order modes Image reject Mixer Amplifier LO 6446 MHz Eliminate RF Low Noise 3 GHz Low pass filter 20dB preamplifier 20MHz Low cost PC board construct for quantity production 6dB noise figure, 70dB linearity measured 27nm RMS noise at ATF2 High IP3 12dB amplifier Anti-alias filter 40MHz low pass 100Ms/s 14 bit digitizer 35

36 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! 36

37 CTF3 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 BPM Signal RF Signals 37

38 LHC Synchrotron Light Monitor Two applications: Two particle types: 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. 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 38

39 LHC Cryostat 70 m 194 mm To arc To RF cavities and IP4 1.6 mrad 420 mm D4 10 m D3 Extracted light sent to an optical table below the beamline U mm 26 m 937 mm

40 LHC Synchrotron LIght monitor Works! Horizontal 0.68 mm 0.70 mm Vertical 0.56 mm 1.05 mm Light from D3 dipole. Blue filter. Narrow slit. This Fall: Synchtrotron light images from...lead! 40

41 Other Stuff Dark matter "Heavy Photon" search at Jeffreson lab Timing system for forward proton detector at LHC Design / tests for thin high average power W target. (C. Field) 1ps timing over 500M in high radiation environment. NLCTA: Obvious place for APE to work, but so far too manpower limited 41

42 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. 42