A decade-long effort at the Advanced Photon Source (APS) of Argonne National Laboratory (ANL) on development of superconducting undulators culminated in December 2012 with the installation of the first superconducting undulator "SCU0" into Sector 6 of the APS storage ring. The device was commissioned in January 2013 and has been in user operation since. This paper presents the magnetic and cryogenic design of the SCU0 together with the results of stand-alone cold tests. The initial commissioning and characterization of SCU0 as well as its operating experience in the APS storage ring are described.

Development of superconducting undulators continues at the Advanced Photon Source (APS). Two years after successful installation and commissioning of the first relatively short superconducting undulator "SCU0" in Sector 6 of the APS storage ring, the second 1.1-m-long superconducting undulator "SCU1" was installed in Sector 1 of the APS. The device has been in user operation since its commissioning in May 2015. This paper describes the magnetic and cryogenic design of the SCU1 together with the results of stand-alone cold tests. The SCU1's magnetic and cryogenic performance as well as its operating experience in the APS storage ring are also presented.

We report observations of an intense sub-THz radiation extracted from a ∼3 MeV electron beam with a flat transverse profile propagating between two parallel oversized copper gratings with side openings. Low-loss radiation outcoupling is accomplished using a horn antenna and a miniature permanent magnet separating sub-THz and electron beams. A tabletop experiment utilizes a radio frequency thermionic electron gun delivering a thousand momentum-chirped microbunches per macropulse and an alpha-magnet with a movable beam scraper producing sub-mm microbunches. The radiated energy of tens of microJoules per radio frequency macropulse is demonstrated. The frequency of the radiation peak was generated and tuned across two frequency ranges: (476-584) GHz with 7% instantaneous spectrum bandwidth, and (311-334) GHz with 38% instantaneous bandwidth. This prototype setup features a robust compact source of variable frequency, narrow bandwidth sub-THz pulses.

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To realize and test advanced accelerator concepts and hardware, a beamline is being reconfigured in the Linac Extension Area (LEA) of APS linac. A photo-cathode RF gun installed at the beginning of the APS linac will provide a low emittance electron beam into the LEA beamline. The thermionic RF gun beam for the APS storage ring, and the photo-cathode RF gun beam for LEA beamline will be accelerated through the linac in an interleaved fashion. In this paper, the design studies for interleaving lattice realization in APS linac is described with initial experiment result. development of compact free electron lasers (FELs). SBWAs or plasma wakefield accelerators with SRF injectors are good candidates for multi-user compact FELs with a high repetition rate [1].A critical requirement to realize SBWAs is to extract maximum power up to 80 % from drive bunches, and to obtain the highest energy for the witness bunch. A total of four times energy gain can typically be gained by witness electrons in SBWA, because the transformer ratio is five in the case of triangle distribution, assuming 80 % efficiency. Some activities of SBWAs for compact X-ray FELs are being conducted in ANL [2] and the development and test of a 0.5 m long acceleration unit are planned in the Linac Extension Area (LEA) tunnel downstream of the APS injector linac [3]. The APS linac [4,5] is part of the injector complex of the APS storage ring. The thermionic RF electron gun (RG) provides the electron beam that is accelerated through the linac, injected into the Particle Accumulator Ring (PAR), cooled, and transferred to the Booster synchrotron. It is then accelerated, and injected into the APS storage ring. The linac is also equipped with a state-of-the-art S-band Photo-Cathode Gun (PCG). Three fast-switching dipole magnets at the end of the linac (so-called interleaving dipoles) direct the electron beam in and out of the PAR and into the Booster. Turning them off allows the beam to bypass the PAR and Booster and direct electrons into the LEA tunnel that follows the APS linac. The LEA beamline is being configured for the testing of small-aperture apparatus and other beam physics experiments that will take advantage of the high brightness beam generated by the PCG.Typically, the beam generated from RG is used ~ 20 seconds every two minutes to support storage ring top-up operation. A relatively quick switching between RG and PCG (interleaving) will allow to operate LEA beamline during the rest of the two minutes. Because of the significantly different properties of beams produced by RG and PCG including beam energy, energy spread, bunch length, emittance and bunch charge, setting up one single lattice for the linac suitable for both beams is extremely challenging. In this paper we present a solution of this problem. Section 2 introduces optimum APS linac lattice for storage ring injection. Section 3 describes the optimum APS linac lattice for PCG and LEA experiments. A compromise interleaving lattice that conserves the high brightness of the PCG generated b...

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The Intense Pulsed Neutron Source (IPNS) Rapid Cycling Synchrotron (RCS) delivers 450-MeV protons in 70 ns pulses at 30 Hz to a heavy-metal target producing spallation neutrons for material science research. The average current extracted from the RCS is 15 µA with a peak intensity of 10 Amps. The large circulating currents in the RCS generate oscillations in the bunch which are presently controlled by modulating the phase of the two rf cavities. By adding second harmonic (SH) rf, the bunch length can be increased reducing the peak current. Simulations suggest that a 20-40 percent increase in extracted current should be achievable. The simulation program allows for phasing between fundamental and SH rf voltages. Initial studies to optimize phase indicate the need to maximize bucket area early in the acceleration cycle, whereas bunching factor is more significant later in the cycle.