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G. Travish FAC Meeting 28OCT05 The LCLS BC1 Bunch Length Monitor System Eric Bong 1 Mike Dunning 2 Paul Emma 1 Patrick Krejcik.

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Presentation on theme: "G. Travish FAC Meeting 28OCT05 The LCLS BC1 Bunch Length Monitor System Eric Bong 1 Mike Dunning 2 Paul Emma 1 Patrick Krejcik."— Presentation transcript:

1 G. Travish FAC Meeting 28OCT05 The LCLS BC1 Bunch Length Monitor System Eric Bong 1 Mike Dunning 2 Paul Emma 1 Patrick Krejcik 1 Tim Montagne 1 Jamie Rosenzweig 2 Gil Travish 2 Juhao Wu 1 1 SLAC | 2 UCLA

2 G. Travish FAC Meeting 28OCT05 Intro: The Problem The LCLS demands tight beam parameters Longitudinal feedback systems needed (along with other diagnostics and feedback systems) Bunch length Energy This is a critical diagnostic Machine wont work without this Has to operate 24-7 Need to start addressing safety and approval issues Time is short

3 G. Travish FAC Meeting 28OCT05 Intro: The Approach UCLA to build bunch length monitor system System will consist of two grating polychromators, one at each bunch compressor Simulations to determine start-end response of monitor. SLAC to integrate into beamline Working on testing at and with ANL-APS

4 G. Travish FAC Meeting 28OCT05 Introduction

5 G. Travish FAC Meeting 28OCT nC0.2 nC Relevant Parameters Nominal electron energy, BC10.25 GeV Nominal electron energy, BC24.3 GeV Peak current A Nominal RMS bunch length, BC120060µm Nominal RMS bunch length, BC2208µm Nominal RMS bunch duration, BC fs Nominal RMS bunch duration, BC26727fs Max single bunch repetition rate120 Hz

6 G. Travish FAC Meeting 28OCT05 Intro: Possible Solutions Streak Camera Interferometer Electro-Optic Techniques RF Deflecting Cavity Polychromator (Spectrometer) ______(fill in your favorite method here)

7 G. Travish FAC Meeting 28OCT05 * LCLS PRD. # J. Wu et al., SLAC-PUB-11276, May Intro: System Requirements * Only relative bunch length needed- not absolute bunch length Need two bunch length monitors- one at each bunch compressor # Single-shot Non-invasive Maintenance free for several days Maximum repetition rate: 120 Hz Measurement resolution: 1-2 % of nominal bunch length (sub-femtosecond) Long term signal drift: <2% over ~24 hours

8 G. Travish FAC Meeting 28OCT05 Observables - Bunch length z - Energy E Controllables - Linac voltage V rf - Linac phase rf LCLS longitudinal feedback has 2 bunch length loops Feedback model studied by Wu, et al., SLAC-PUB-11276, May Conceptual Schematic of single loop Intro: Phase Feedback

9 G. Travish FAC Meeting 28OCT05 Hamamatsu "FESCA-200 (Femtosecond Streak Camera). Temporal resolution: 200 fs. Possible Solutions Streak Cameras + Single-shot + Wide dynamic range - Limited temporal resolution (~200 fs at best) - Trigger jitter

10 G. Travish FAC Meeting 28OCT05 Possible Solutions Interferometers + Can be single-shot ? Sufficient temporal (frequency) resolution + Compact - Narrow dynamic range - Complex

11 G. Travish FAC Meeting 28OCT05 Electro-Optic Methods + Single-shot ? Non-invasive ? Temporal resolution - Not yet mature - Require expensive femtosecond lasers Possible Solutions P. Bolton et al., SLAC-PUB Transverse probe geometry produces a spatial image of the bunch. Also see:

12 G. Travish FAC Meeting 28OCT05 RF Deflecting Cavities + Single shot ? Temporal resolution - May require separate RF system - Invasive (destroy measured shot) Possible Solutions The UCLA 9-cell X-band standing wave deflecting cavity. Courtesy Joel England.

13 G. Travish FAC Meeting 28OCT05 Possible Solutions Polychromators + Single-shot + Temporal resolution + Robust -Require relatively expensive detector & vacuum system

14 G. Travish FAC Meeting 28OCT05 BC1 Single-Shot Spectrometer After 4th magnet CSR port Narrow angle Magnet just upstream

15 G. Travish FAC Meeting 28OCT05 Single-Shot Spectrometer Use CSR/CER from bunch compressor chicane magnets Vacuum port window Focusing/turning mirror Entrance slit Grating Off-axis parabola (line focus) Multichannel detector Cryostat & Bolometers Basic Design Line focus mirror

16 G. Travish FAC Meeting 28OCT05 The Selection: Polychromator Spectrums are very reliable; no dependence on amplitude (charge) or intricacies of pulse shape. Speed, bandwidth and phase noise not an issue. Robust (0-2 moving parts) Proven Simple Easy to model and easy to fix

17 G. Travish FAC Meeting 28OCT05 Single-Shot Spectrometer Bunch Distributions BC1BC2 Smooth parabolic distribution + Simple CSR spectrum Wake-induced double-horn - Complicated CSR spectrum Courtesy P. Emma

18 G. Travish FAC Meeting 28OCT05 UCLA Simulations TREDI Post-processor: FieldEye Calculate far field radiation pattern using Lenard-Wiechert algorithm Fourier analysis Angular spectrum Dependent on TREDI TREDI: time intensive Flexibility in post-processing Other applications Coherent Transition Radiation Coherent Cerenkov radiation Sample CSR spectrum calculation using FieldEye

19 G. Travish FAC Meeting 28OCT05 Related CER Work (at BNL - ATF) UCLA built ATF compressor. Brookhaven Si Bolometer for CER detection. FieldEye calculated spectrum for 20 micron long beam, 1000 particles, edge radiation in chicane

20 G. Travish FAC Meeting 28OCT05 Challenge: Beamline Integration Low-loss vacuum port window over desired frequency range (Diamond) Cryostats: liquid helium & nitrogen Helium hold time (weeks?) Closed-cycle nitrogen system (Sterling Engine?) Room temperature alternative? Windowless enclosure for detector system

21 G. Travish FAC Meeting 28OCT05 Central Issue: Flat response curve over THz Materials: Z-cut crystalline quartz Silicon HDPE PTX (polymethylpentene) Diamond References: SLAC-PUB Vacuum Port Window Materials & Issues

22 G. Travish FAC Meeting 28OCT05 Diamond Vacuum Port Window Absorption Curve

23 G. Travish FAC Meeting 28OCT05 Harris International: Fraunhofer: EOC (Electro Optical Components): Diamond Vacuum Port Window Vendors

24 G. Travish FAC Meeting 28OCT05 ~100 mm OAP focusing/turning mirrorOAP line focus mirror ~100 mm ~250 mm Mirrors Conventional: gold coated copper Here: could be CNC aluminum

25 G. Travish FAC Meeting 28OCT05 Mirrors Vendors Kugler of America: Reynard Corp.: Janos Tech: CVI Optical Components: Janos Tech Kugler of America

26 G. Travish FAC Meeting 28OCT05 ~150 mm Grating Machined Copper Blazed Groove width ~1 mm To be optimized

27 G. Travish FAC Meeting 28OCT05 BC1 Frequency range: GHz ~ 20 channels Easy, but big large vacuum chamber large optics InSb hot electron bolometers BC2 Frequency range: 1-4 THz ~ 20 channels More challenging than BC1 Needs special filtering Thermal composite bolometers? Need to research more Challenge: Detectors

28 G. Travish FAC Meeting 28OCT05 + Speed + Sensitivity -Cryo-cooling Cryostat hold time -Expensive Vendors QMC Instruments: IR Labs: Detectors Bolometers

29 G. Travish FAC Meeting 28OCT05 + Relatively inexpensive + Speed - Sensitivity - Resonances Vendors EOC: Fuji & Co.: Detectors Pyroelectric

30 G. Travish FAC Meeting 28OCT05 + Less expensive than bolometers -Speed (25 Hz) -Noise sensitivity -Size Vendors QMC Instruments: Tydex: Detectors Golay Cells

31 G. Travish FAC Meeting 28OCT05 + Inexpensive + Speed -Frequency response -Sensitivity Vendors Virginia Diodes: Advanced Control Components: Detectors Diodes

32 G. Travish FAC Meeting 28OCT05 20-channel linear array of InSb hot-electron bolometers, courtesy QMC Instruments. 250 mm InSb hot-electron bolometers 10 liter cryostat Helium hold time: 4-6 weeks! Detector blocks with Winston Cones and Filters BC1 Detector Assembly

33 G. Travish FAC Meeting 28OCT05 Testing LCLS BC1 is most similar to the APS LEUTL Bunch Compressor. Propose collaboration with ANL on testing. Rapid installation of window and turning mirror (site specific) during proximate access. Installation of polychrometer as assembly.

34 G. Travish FAC Meeting 28OCT05 What will we test Beam energy, energy spread, charge and bunch length can mimic LCLS design. Simulations can be confirmed for a range of bunch lengths. Noise, dynamic range in amplitude (charge) and bunch length. Hard to test: feedback

35 G. Travish FAC Meeting 28OCT05 Project Start

36 G. Travish FAC Meeting 28OCT05 Project Overview

37 G. Travish FAC Meeting 28OCT05 Schedule Issues Theory: behind on simulations Acquisition: driven by detector Testing: can you install and test anything in 2 months? Delivery: November 2006 Post delivery: beamline integration, safety issues, etc.

38 G. Travish FAC Meeting 28OCT05 Conclusions Simulations behind schedule Subcomponent selection proceeding well Challenging schedule can be addresses with APS collaboration, better coordination with SLAC, and timely funding. Hardware cost and schedule driven by detector Beamline integration needs to be considered now

39 G. Travish FAC Meeting 28OCT05 End

40 G. Travish FAC Meeting 28OCT05 Possible Solutions Summary Single-shotNon- Invasive Sufficient Temporal Resolution Maintenance Free Streak CameraYYNY InterferometerYY?N Electro-OpticY??? RF DeflectorYN?N PolychromatorYYYY PBPL

41 G. Travish FAC Meeting 28OCT05 Single-Shot Spectrometer Challenge: BC2 CSR Spectrum CSR energy spectrum after BC2. Black curve: double-horn distribution Blue curve: Gaussian distribution Red curve: step function From J. Wu, et al., SLAC-PUB-11275, May Double-horn distribution complicates CSR spectrum - Similar to Gaussian below 4 THz - Wu: Stay below 4 THz

42 G. Travish FAC Meeting 28OCT05 Workplan Simulate CR exiting vacuum ports of BC1, BC2 & arriving at detector TREDI/FieldEye simulations Choose detector type Finalize bolometer evaluations Continue to study system Formation length (source to detector distance) Dynamic range (grating, in situ tuning) Calibration methods Mechanical design & beamline integration with SLAC CAD design work Finalized by SLAC Test system (SPPS or APS Linac)


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