Dean Walters

FEL development at the Advanced Photon Source

Construction of a single-pass free-electron laser (FEL) based on the self-amplified spontaneous emission (SASE) mode of operation is nearing completion at the Advanced Photon Source (APS) with initial experiments imminent. The APS SASE FEL is a proof-of-principle fourth-generation light source. As of January 1999 the undulator hall, end-station building, necessary transfer lines, electron and optical diagnostics, injectors, and initial undulators have been constructed and, with the exception of the undulators, installed. All preliminary code development and simulations have also been completed. The undulator hall is now ready to accept first beam for characterization of the output radiation. It is the project goal to push towards full FEL saturation, initially in the visible, but ultimately to UV and VUV, wavelengths.

Design and performance of the LCLS cavity BPM system

In this paper we present the design of the beam position monitor (BPM) system for the LCLS undulator, which features a high-resolution X-band cavity BPM. Each BPM has a TM010 monopole reference cavity and a TM110 dipole cavity designed to operate at a center frequency of 11.384 GHz. The signal processing electronics features a low- noise single-stage three-channel heterodyne receiver that has selectable gain and a phase locking local oscillator. We will discuss the system specifications, design, and prototype test results.

APS storage ring vacuum system performance

The Advanced Photon Source (APS) storage ring was designed to operated with 7-GeV, 100-mA positron beam with lifetimes >20 hours. The lifetime is limited by residual gas scattering and Touschek scattering at this time. Photon-stimulated desorption and microwave power in the RF cavities are the main gas loads. Comparison of actual system gas loads and design calculations will be given. In addition, several special features of the storage ring vacuum system will be presented.

Design Improvement and Bias Voltage Optimization of Glass-Body Microchannel Plate Picosecond Photodetector

Microchannel plate photodetectors, capable of picosecond time resolution and sub-mm spatial resolution, are a perfect candidate for the next generation of photodetectors for precision timing measurements. Argonne National Laboratory is producing low-cost, all-glass body, planar photodetectors with an indium seal. The design and fabrication of 6-cm square photodetectors has been well demonstrated in an ultra-high vacuum system. Recently, a new design was developed to optimize the photodetector bias voltage. This design offers an improved configuration and allows external control of the bias voltage for each internal detector component. Design and measurements of the new independently biased devices are described in this paper. We performed a systematic study on the bias voltage and achieved a gain on the order of

MCP-based photodetectors for cryogenic applications

10^{{\mathbf {7}}}

Coatings for the APS RF cavity tuners for the reduction of secondary electrons

, a time resolution better than 35 ps, and a spatial resolution better than 1 mm.

Beam chopper for the low-energy undulator test line (LEUTL) in the APS

The Argonne MCP-based photo detector is an offshoot of the Large Area Pico-second Photo Detector (LAPPD) project, wherein 6 cm x 6 cm sized detectors are made at Argonne National Laboratory. We have successfully built and tested our first detectors for pico-second timing and few mm spatial resolution. We discuss our efforts to customize these detectors to operate in a cryogenic environment. Initial plans aim to operate in liquid argon. We are also exploring ways to mitigate wave length shifting requirements and also developing bare-MCP photodetectors to operate in a gaseous cryogenic environment.

Recent progress in the development of 6 cm × 6 cm micro-channel plate based photodetectors at Argonne National Laboratory

Thin film coatings are used to reduce the generation of secondary electrons at the ends of the Advanced Photon Source (APS) RF cavity tuners because these electrons result in increased temperatures on the tuner. To improve the film properties over the existing evaporated titanium film, a magnetron-sputtered film of titanium nitride has been developed that is both harder and adheres more strongly than the past evaporated film. This paper describes the process for creating this new coating.

Modular component positioning along the beamline axis

The low-energy undulator test line (LEUTL) is being built and will be tested with a short beam pulse from an rf gun in the Advanced Photon Source (APS) at the Argonne National Laboratory. In the LEUTL a beam chopper is used after the rf gun to deflect the unwanted beam to a beam dump. The beam chopper consists of a permanent magnet and an electric deflector that can compensate for the magnetic deflection. A 30-kV pulsed power supply is used for the electric deflector. The chopper subsystem was assembled and tested for beamline installation. The electrical and beam properties of the chopper assembly are presented.

Aluminum coating in the undulator vacuum chamber for the Linac Coherence Light Source

Argonne National Laboratory (ANL) is currently developing 6 cm × 6 cm, all-glass body, sealed photodetectors based on Microchannel Plates (MCPs) functionalized by Atomic Layer Deposition (ALD). A Small Single Tube Processing System (SmSTPS) was constructed for fabricating the photodetectors. A number of first version devices were successfully produced and have shown satisfactory performances. Recently, a new version of these devices based on an Independently Biased Design (IBD) was developed. This design allows for individually controlling the voltage of each stack component to optimize the performance. So far, six IBD devices have been produced and characterized. We have measured 14% Quantum efficiency, 107 gain and 35 ps overall time resolution including the laser jitter. In this paper, we present the status of the tube production, the photodetector design and the testing results.