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

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

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.

4 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

5 TCAV Bunch Length Measurement Transverse cavity provides time dependent kick Optics for 90 degree phase advance Longitudinal transformed to transverse Profile monitor 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. Loos

6 LCLS Short Bunches Operate 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° phase1°phase No LasingGood lasing

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 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, /C° temperature coefficient -> 10ps/C° (!) Raw Signal Phase slope gives cavity temperature

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

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.

11 Full Timing System 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

13 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

14 Future Timing Electronic 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

15 “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

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

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 (10 6 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 pump Low charge FEL bunch for X-ray probe

18 THz System Simulation by H. Loos A. Fisher, A. Lindenberg (PULSE) ~3V/Å Electric Field Lab source:.01V/Å Experiment laser 800nm 20fs pulses 68 MHz, 150mW Characterize THz, then use for experiments

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

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 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

21 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

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 M. Woodley

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

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

25 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

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

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)

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

30

31 ATF2

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.

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, requires 10nm beam position measurement.

34 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 resolution 15um range 50nm drif 1 hour

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

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!

37 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

38 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

39 LHC

40 LHC Synchrotron LIght monitor Works! This Fall: Synchtrotron light images from....LEAD!

41 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

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.