Accelerator Overview
•Goals for proposal
•Description of technical components: injector,
linac, compressors, etc.
•Summary of technical challenges
•Elements of R&D program
William S. Graves
MIT-Bates Laboratory
Presentation to MIT X-ray laser
Accelerator Science Advisory
Committee
September 18-19, 2003
W.S. Graves, ASAC Review, Sept 18-19, 2003
Goals for proposal
1. Describe an integrated laser laboratory integrating sources that span
the visible to x-ray wavelengths.
2. Produce accelerator and laser design for a user facility.
3. Increase the user community’s perception that required accelerator
and laser technologies are mature.
Three key attributes:
1. Many beamlines are planned, each running at 1 kHz or more.
2. Laser wavelengths spanning visible to x-ray are available in a single
facility.
3. Seeding for longitudinal coherence at all wavelengths is included in the
initial design.
W.S. Graves, ASAC Review, Sept 18-19, 2003
A brief history of the MIT effort
•Spring 2002
D. Moncton approaches R. Milner about the possibility of an x-ray
FEL at Bates lab.
•Summer 2002
Workshop held at Bates on the source technologies.
•Spring 2003
Proposal for 4 GeV user facility submitted to NSF.
Collaboration meeting held for contributors to proposal.
•Summer 2003
User program committee meets.
•Fall 2003
First accelerator concept review. Today!
W.S. Graves, ASAC Review, Sept 18-19, 2003
Technical Components
1. High repetition rate photoinjector, cathode, drive laser.
2. SRF sections, preferably CW, including 3rd harmonic cavity.
3. Bunch compressors.
4. Electron beam switchyard to undulator halls.
5. Seed lasers, HHG generation.
6. FEL output properties, undulator layout.
Little presentation on x-ray components and diagnostics, or
electron beam diagnostics.
W.S. Graves, ASAC Review, Sept 18-19, 2003
Facility layout
Master oscillator
Fiber link synchronization
UV Hall X-ray Hall
Seed Pump Seed Pump
laser laser laser laser
Undulators
100 nm
Undulators
30 nm 1 nm
Injector
laser 10 nm 0.3 nm
SC Linac 0.3 nm SC Linac 0.1 nm
1 GeV 2 GeV 4 GeV
10 nm
Future upgrade to 0.1
nm at 8 GeV
3 nm
1 nm
Undulators
Seed Pump
laser Nanometer Hall laser
W.S. Graves, ASAC Review, Sept 18-19, 2003
Key accelerator elements and issues
Bunch
compressor Seed laser
Photoinjector
Ebeam
SRF linac SRF linac
switch
Undulators
Photocathode Photocathode laser: Timing and power stability
laser
Photoinjector: Produce low emittance ebeam at 5% duty factor
Linac: Rf amplitude and phase
Compressor: Produce high peak current ebeam, low CSR.
Switch: Rate, stability
Undulators: Tunability, variable length
Seed lasers: HHG generation, stable operation, timing
W.S. Graves, ASAC Review, Sept 18-19, 2003
Photoinjector
3 cell pulsed room temperature cavity operating at 10 kHz
-presentation by Manouchehr Farkhondeh
W.S. Graves, ASAC Review, Sept 18-19, 2003
Photoinjector drive laser
Direct diode-pumped, fiber amplifier
-presentation by Franz Kaertner
Temporal: Flat-top shaped
Yb:fiber amplifier
IPG-Photonics
Yb:YAG, Acousto-Optic
Programmable 20ps, 10mJ, 1-10 kHz
1ps Pulse Pulse Shaper @ 1064 nm
rep. Rate Selector (Dazzler,
100 MHz Fastlight) 4th-Harmonic
20ps, 1mJ, 1-10 kHz
@266 nm
W.S. Graves, ASAC Review, Sept 18-19, 2003
RF and cryoplant
RF Control Block Diagram
Quad
Mixer
Cavity
Q I
RF Source-loop
Electronics
Phase
Shifter
Vector Demodulator RF Source
Optical Master Oscillator Elec. Quad
Mode-Locked Laser Optic Mixer
I Q Digital Attenuator
Phase
Shifter
Synchrotron Cavity-Loop
Light / BPM Electronics
I Q
Phase
Quad Shifter
Mixer
Vector Modulator
-presentation by Townsend Zwart
W.S. Graves, ASAC Review, Sept 18-19, 2003
Beam dynamics, bunch compression
-presentation by Fuhua Wang
W.S. Graves, ASAC Review, Sept 18-19, 2003
Electron beam switchyard
Undulator, Beam Line Hall
RF/Ferrite switch, 5 mr
Septum Magnet, 150 mr
Dipole Magnet, 350 mr
Undulator
10 20 30
Accelerator
0 10 20 30 40 50 m
-presentation by Jan van der Laan
W.S. Graves, ASAC Review, Sept 18-19, 2003
Laser seeding
Noble Gas Jet (He, Ne, Ar,
Kr)
100 mJ - 1 mJ XUV @ 3 – 30
nm
@ 800 nm
h = 10-8 - 10-5
t Propagation
Recombination
Cut-off Harmonic:
0
wXUV x
tb
-Wb N cw 0 Wb 3.17U p (t )
Ionization
Energy
Laser electric field
-presentation by Franz Kaertner
W.S. Graves, ASAC Review, Sept 18-19, 2003
FEL output properties
2 2 8
7
1.5 1.5 6
Power (GW)
Power (GW)
Power (GW)
5
1 1 4
3
0.5 0.5 2
1
0 0 0
0 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50
Time (fs) Time (fs)
Time (fs)
1000 500 500
Power (MW/bin)
800 400 400
Power (kW/bin)
Power (kW/bin)
600 300 300
400 200 200
200 100 100
0 0 0
0.2995 0.3 0.3005 0.301 0.2995 0.3 0.3005 0.301 0.2995 0.3 0.3005 0.301
Wavelength (nm) Wavelength (nm)
Wavelength (nm)
Seeding for short Seeding for SASE
pulses narrow bandwidth
W.S. Graves, ASAC Review, Sept 18-19, 2003
Technical challenges
1. Achieve ~10 fs timing synchronization between FEL output, seed
lasers, and pump-probe lasers.
2. Necessary RF phase and amplitude stability for timing above.
3. Stability in energy per pulse, timing, and pointing appropriate for
a user facility.
4. Reduced power consumption for CW operation.
5. Reliable laser seed generation including tunability and stability.
6. Development of fast RF or ferrite switches necessary to deliver
beam to multiple undulators.
7. Development of a high repetition rate, high brightness
photoinjector.
8. Development of tunable undulators. Matching of undulator
resonance. Rapid orbit correction at different wavelengths.
9. Electron beam diagnostics.
10. Coherent photon beam diagnostics.
W.S. Graves, ASAC Review, Sept 18-19, 2003
NSF referee reports
•Proposal covers very large range of activities…difficult for individuals to
review.
•Several referees recommend stronger R&D program.
•Doubts expressed about maturity of technologies.
•Reviews and our response to specific issues will be discussed Fri a.m.
Provide your input and feedback on the reviews and our response. Give
advice on R&D issues and effort level.
Is substantial R&D necessary before proceeding to design stage?
Identify best path forward.
MIT remains committed to
building an x-ray laser lab
W.S. Graves, ASAC Review, Sept 18-19, 2003
R&D program at Bates
Demonstrate some of the key technologies at lower energy including
1. Seeding with ultrashort HHG pulses
2. Development of tunable seed laser
3. Cascaded HGHG FEL output
4. Timing synchronization of FEL, seed, and pump lasers below 100 fs
Identify key R&D issues.
W.S. Graves, ASAC Review, Sept 18-19, 2003
Original schedule
W.S. Graves, ASAC Review, Sept 18-19, 2003
Concluding remarks
•Concept is still at an early stage.
•Simulations of separate systems (injector, linac, switchyard,
FEL) are underway, but not yet connected as a start-to-end
effort.
•This review should assess the directions we are taking rather
more than the initial results.
W.S. Graves, ASAC Review, Sept 18-19, 2003