Abstract
At the electron linac for beams with high brilliance and low emittance (ELBE) center for high-power radiation sources, the second version of a superconducting radio-frequency (SRF) photoinjector has been put into operation and has been routinely applied for user operation at the ELBE electron accelerator. SRF guns are suitable for generating a continuous wave electron beam with high average currents and high beam brightness. The SRF gun at ELBE has the goal to generate short electron pulses with bunch charges of 200–300 pC at typical repetition rates of 100 kHz for the production of superradiant, coherent terahertz radiation. The SRF gun includes a 3.5-cell, 1.3-GHz niobium cavity and a superconducting solenoid. A support system with liquid nitrogen (LN2) cooling allows the operation of normal-conducting, high quantum efficiency photocathodes. We present the design and performance of the SRF gun as well as beam measurement results of the operation with Mg photocathodes at an acceleration gradient of 8 MV/m (4 MeV kinetic energy). In the last section, we discuss the SRF gun application for production of coherent terahertz radiation at the ELBE facility.
Highlights
The “electron linac for beams with high brilliance and low emittance (ELBE)” is a user facility open for international research projects with electrons and secondary radiation
At the electron linac for beams with high brilliance and low emittance (ELBE) center for high-power radiation sources, the second version of a superconducting radio-frequency (SRF) photoinjector has been put into operation and has been routinely applied for user operation at the ELBE electron accelerator
We present the design and performance of the SRF gun as well as beam measurement results of the operation with Mg photocathodes at an acceleration gradient of 8 MV=m (4 MeV kinetic energy)
Summary
The “electron linac for beams with high brilliance and low emittance (ELBE)” is a user facility open for international research projects with electrons and secondary radiation. For the ELBE facility, a thermionic dc gun of 235 kV routinely provides up to 77 pC at 13 MHz. for the high-power IR free-electron lasers (FELs) and other users. As part of the R&D effort to explore a new cw injector for the ELBE center, the first SRF gun was developed and operated from 2007 to 2014 as the second injector [9] This gun consisted of a 1.3-GHz 3.5-cell niobium cavity, a choke filter with a normal conducting photocathode, a drive laser, a beam transport system, and all other accessories. The advantages of the ELBE SRF gun II are the high field gradient, the high duty factor beam operation due to its superconducting technology, and the good vacuum conditions suitable for sensitive photocathodes. SRF guns are suitable to be used in other applications, such as energy recovery linac projects [12], high duty factor x-ray FELs [13], and MeV ultrafast electron diffraction and microscopy [14]
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