Experimental results from the Los Alamos FEL photoinjector

Feldman, D. W.; Bender, Steven C.; Carlsten, Bruce E.; Early, J.W.; Feldman, Robert; Johnson, W. Joel D.; Lumpkin, A.H.; O’Shea, P.G.; Stein, William E.; Sheffield, R.L.; Young, L.M.

doi:10.1109/3.104143

Cited by 35 publications

(9 citation statements)

References 10 publications

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“…Previous photocathode RF gun experiments have operated at 3 GHz or below [2][3][4][5][6][7][8][9][10], though an RF gun experiment at 8.5 GHz is currently under development [11]. There has also been much theoretical work in the study of RF guns in recent years [12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical investigations of a 17GHz RF gun

Brown

Trotz

Kreischer

et al. 1999

Nuclear Instruments and Methods in Physics Research Section A:

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We report on experimental and theoretical investigations of a 17 GHz RF photocathode electron gun. This is the first photocathode electron gun to operate at a frequency above 2.856 GHz. The 1.5 cell, π−mode, copper cavity was tested with 50 ns pulses from a 17.150 GHz klystron amplifier built by Haimson Research Corp. A Bragg filter was used at the RF gun to reduce the reflection of parasitic modes back into the klystron. Coupling hole theory in conjunction with cold test measurements was used to determine the field profile in the RF gun. The particle in cell code MAGIC as well as coupled envelope equations were used to simulate the beam dynamics in the RF gun. With power levels of 4 MW, the on axis electric field at the cathode exceeds 300 MV/m, corresponding to an average accelerating gradient of 200 MV/m over the first half cell of the gun. Breakdown was observed at power levels above 5 MW. Electron bunches were produced by 20 µJ, 1 ps UV laser pulses impinging on the RF gun copper photocathode and were measured with a Faraday cup to have up to 0.1 nC of charge. This corresponds to a peak current of about 100 A, and a density at the cathode of 8.8 kA/cm 2 . Multiple output electron bunches were obtained for multiple laser pulses incident on the cathode. Phase scans of laser induced electron emission reveal an overall phase stability of better than ±20°, corresponding to ±3 ps synchronization of the laser pulses to the phase of the microwave field. A Browne-Buechner magnetic spectrometer indicated that the RF gun generated 1MeV electrons with a single shot rms energy spread of less than 2.5%, in good agreement with theoretical predictions.3

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Section: Introductionmentioning

confidence: 99%

Experimental and theoretical investigations of a 17GHz RF gun

Brown

Trotz

Kreischer

et al. 1999

Nuclear Instruments and Methods in Physics Research Section A:

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“…Among the various possibilities, the photoelectric process is very promising for getting easily electron beam of high current and low emittance. In fact, experimental results have confirmed that pulsed electron beams obtained by photocathodes are characterized by emittances much better than those achievable by thermionic guns [6,7], resulting, as a consequence, in a large brightness.…”

Section: Introductionmentioning

confidence: 61%

Photo-emission studies from Zn cathodes under plasma phase

Belloni¹,

Caretto²,

Lorusso³

et al. 2005

Radiation Effects and Defects in Solids

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In this paper, we report investigations of the electron emission from pure Zn cathodes irradiated by UV laser pulses of 23 ns (full-width at half-maximum) at a wavelength of 248 nm (5 eV). The metal cathodes were tested in a vacuum photodiode chamber at 10 −5 Pa. They were irradiated at normal incidence and the anode-cathode distance was set at 3 mm. The maximum applied accelerating voltage was 18 kV, limited by the electrical breakdown of the photodiode gap. Under the above experimental conditions, a maximum applied electric field of 6 MV/m resulted. In the saturation regime, the measured quantum efficiency value increased with the accelerating voltage due to the plasma formation. The highest output current was achieved with 14 mJ laser energy, 18 kV accelerating voltage and its value was 12 A, corresponding to a global quantum efficiency (GQE) approximately of 1 × 10 −4 . The temporal quantum efficiency was 1.0 × 10 −4 at the laser pulse onset time and 1.4 × 10 −4 at the pulse tail. We calculated the target temperature at the maximum laser energy. Its value allowed us to obtain output pulses of the same laser temporal profile. Tests performed with a lower laser photon energy (4.02 eV) demonstrated a GQE of two orders of magnitude lower.

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“…Electron beams can be obtained by different processes. The thermionic process is the most known but the photoelectric one seems to be very promising for getting easily electron beams of high current of low emittance [5,6]. Consequently, these characteristics should promise the best background in helping high brightness electron beams.…”

Section: Introductionmentioning

confidence: 99%