George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This...
-
Upload
nigel-hamlin -
Category
Documents
-
view
216 -
download
3
Transcript of George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This...
![Page 1: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/1.jpg)
George Neil and Gwyn Williams
JSA Science Council
January 7, 2011
UV FEL Status and Plans
* This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150, the Air Force Office of Scientific Research, DOE Basic Energy Sciences, the Office of Naval Research, and the Joint Technology Office.
![Page 2: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/2.jpg)
Slide 2
Existing JLab IR/UV Light Source
E = 135 MeV present limitUp to135 pC pulses @ 75 MHz
20 μJ/pulse in (250)–700 nm UV-VIS 120 μJ/pulse in 1-10 μm IR1 μJ/pulse in THz
The first high current ERL14 kW average power
Ultra-fast (150 fs)
Ultra-bright
![Page 3: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/3.jpg)
Initial UV FEL Specifications
Specification from UV Demo proposal (May, 1995)
. Average Power > 1000 W
. Wavelength range 1–0.25 mm
. Micropulse energy ~25 mJ
. Pulse length ~0.1-1 ps FWHM nominal
. PRF 74.85, 37.425, 18.7, 9.36, 4.68
MHz
. Bandwidth ~ 0.2–1.5 %
. Timing jitter < 1 ps
. Amplitude jitter < 2 % p-p
. Wavelength jitter 0.02% RMS
. Polarization linear, > 100:1
. Transverse mode quality < 2x diffraction limit
. Beam diameter at lab 2 - 3 cm
![Page 4: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/4.jpg)
Initial UV FEL Performance
IR FEL UV FEL UV FEL3rd Harmonic
UV FEL5th Harmonic
Photon energy range of fundamental
0.1 – 1.4 eV, (12 -0.8 microns)
1 – 3.4 eV(1200-360 nm)
3-10.2 eV(410-120 nm)
5-17 eV(250-73 nm)
Photon energy per pulse
100 microJoules 20 microJoules 20 nanoJoules 0.2 nanoJoules
Repetition rate 4.678 – 74.85 MHz 4.678 MHz 4.68 MHz 4.68 MHz
Photon Pulse length (FWHM)
100 fs – 2 ps 100 fs – 2 ps 100 fs – 2 ps 100 fs – 2 ps
Nominal pulse bandwidth
1% .2% .2% .2%
Electron Beam Energy 80 – 140 MeV 80 – 140 MeV 80 – 140 MeV 80 – 140 MeV
Charge per electron bunch
135 picoCoulombs 60 picoCoulombs 60 picoCoulombs 60 picoCoulombs
Projected
![Page 5: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/5.jpg)
IR Demo Harmonic Power Measurements
10 -7
10-6
10 -5
0.0001
0.001
0.01
0.1
1
0 1 2 3 4 5 6 7 8
Rel
ativ
e po
wer
Harmonic Number
10-h
Third harmonic power is down by about a factor of 1000. We get about 50 W at 372 nm so we expect about 50 mW of VUV light.
![Page 6: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/6.jpg)
Projected harmonic performance - water cooled mirrors
![Page 7: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/7.jpg)
Working in the UV is challenging • Short wavelengths require higher electron beam energies; the higher the better.
IR Upgrade was fine with 110 MeV; we are limited to 135 MeV at present• The transverse emittance and energy spread needs to be lower by ~ 2X
compared to the IR Upgrade.• Achieve this by operating at ½ the IR Upgrade FEL charge/bunch.
• The vacuum requirement is high and must be achieved to maintain a stable output and avoid mirror degradation.
• Manufacturing mirrors with l/10 figure in the UV is a challenge.• Must also have metrology capable of verifying specs.• Must mount without inducing aberrations.
• UV coatings are more lossy than those in the visible, although exact numbers are hard to pin down. They may be only a few 100 ppm
• We use mirrors with hole outcoupling to let the VUV out. FELs with high gain don’t like this; the mode tries to avoid the hole. A careful match is required for optimal performance
![Page 8: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/8.jpg)
Estimates of FEL performance• Both pulse propagation and one-dimensional spreadsheet models are first
used to estimate the gain and power.
• Gain is (photon power out of wiggler)/(power going in) measured at low power before saturation effects enter the picture
• Efficiency is [1- (ebeam power exiting wiggler)/(ebeam power entering wiggler)] measured at saturation or equivalently (photon power out)/(ebeam power in) if mirror losses are small
![Page 9: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/9.jpg)
400nm 3D simulation results from Genesis/OPC
• Assumes 0.3% energy spread.
Small-signal net gain = 139%Electronic gain = 165%Efficiency = 0.704%
![Page 10: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/10.jpg)
Cornell Undulator A Prototype
![Page 11: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/11.jpg)
UV Demo Commissioning Timeline
• January 2006 - Install and commission Cornell wiggler with new gap mechanism.
• Spring and Summer 2009 – Install beamline components except for optical cavity and wiggler chamber.
• Fall 2009 – CW beam through UV beamline.
• Spring 2010 – Install new zone 3 module and commission.
• June 2010 – Lase at 630 nm, 67 pC in IR laser with 135 MeV beam.
• July 2010 – Recirculate laser quality 1 mA CW beam through wiggler sized aperture.
• August 17, 2010 – First electron beam through wiggler.
• August 19, 2010 – First lasing, 150 W CW at 700 nm.
• August 31, 2010 – First lasing in UV, 140 W @400 nm, 68 W @372 nm
• December 9, 2010 – First measurement of 124 nm light
![Page 12: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/12.jpg)
FEL performance at 700nm
Gain at low power is ~100%, detuning curve is 12.5 µm in length
![Page 13: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/13.jpg)
Images while lasing at 100W
Light scattered from HR mirror
Light scattered from power probe
Power meter
Time dependent diagnostics
![Page 14: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/14.jpg)
FEL performance at 400nm
• We had to run with the OC mirror de-centered, as the metallization technique created a damage spot at the mirror center.
![Page 15: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/15.jpg)
Characterization of 10eV photons
Bob Legg had built a chamber for the SRC at Univ. Wisconsin that we adapted for our purposes:
10eV viewer
Ce:YAG viewer
VUV photodiodeVUV Chamber
Viewport
Just measure diode photoelectric current. No filter required; only responsive to photons > 10 eV. Calibration is traceable to NIST.
![Page 16: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/16.jpg)
Code Comparison with Experiment
• Besides the aforementioned spreadsheet and 1-D pulse propagation codes, we have 3D & 4D codes that better model the FEL interaction.• These codes are: a code developed at NPS, as well as Genesis and
Medusa.• In conjunction with a resonator simulation code we can also model the
effects of aberrations (from thermal absorption, off-axis tilts, etc) and the mode shape within or outside the optical cavity.• This is the Optical Propagation Code (OPC).
• Performance of the UVFEL has greatly exceeded the predictions of simulations.
Parameter Simulations Experiment
Turn-on time 8.6 µsec. 5 µsec.
Gain ~100% ~180%
Detuning curve 4.5 µm >7 µm
Efficiency 0.4-0.7% 0.8%
![Page 17: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/17.jpg)
Very High Gain Seen at 400 nm
![Page 18: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/18.jpg)
from the announcement:
“ 5 nanoJoules of fully coherent light was measured in each 10eV micropulse, which represents approximately 0.1% of the energy in the fundamental, as expected.
These numbers allow us to anticipate being able to deliver 25 - 100 mW by operating CW at up to 4.687 MHz with more optimized water-cooled optics, and several 100's of mW with cryogenically-cooled optics. Optics upgrades, and installation of an optical transport beamline to a user laboratory for full characterization, including bandwidth, are in progress.
We note that for many applications the anticipated narrow bandwidth eliminates the need for a spectrometer. This allows substantially higher flux to be delivered to user experiments than is possible at storage rings. “
![Page 19: George Neil and Gwyn Williams JSA Science Council January 7, 2011 UV FEL Status and Plans * This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150,](https://reader035.fdocuments.us/reader035/viewer/2022070307/551ab3d6550346b2288b4bd5/html5/thumbnails/19.jpg)
What happens next on the UV FEL?
• Present mirror is lossy and hole size is somewhat mismatched for proper outcoupling at these high gains. As a result we cannot lase stably at as high a power as may be possible even with water cooled mirrors. We are obtaining a better water cooled mirror set and will have ROC control.
• We are presently installing Optical Transport to Lab 1 and will test it in February
• We are returning UV wiggler to Cornell and adapting an APS Undulator A at the manufacturer (STI Optronics).
• A high power test in the IR for the ONR will follow in April and early May followed by a shutdown till mid July during which time the cooled mirrors and new undulator will be installed. We will recommission and perform User runs. (Gwyn’s talk)
• We also intend to install a new R100 cryomodule and get higher beam energy for shorter wavelength lasing. Perhaps in June if assembly /installation schedule permits. Lasing in fundamental down to 250 nm may be achievable depending on energy. If not June then October.