R. Heese

Measurement of thermal emittance for a copper photocathode

Measurements of the thermal emittance of an electron beam produced by photoemission from the copper cathode of a high power RF cavity are presented. The RMS normalized emittance has been measured as a function of laser spot size, applied surface field, and polarization of the laser beam at normal incidence. Local field enhancement due to surface effects is found to increase the emittance substantially beyond that expected for a perfect planar surface.

Ultrashort electron bunch length measurements at DUVFEL

The DUVFEL electron linac is designed to produce sub-picosecond, high brightness electron bunches for driving a short wavelength FEL. Four experiments have been commissioned to address the challenge of accurately measuring bunch lengths on this timescale. In the frequency domain, a short 12 period undulator is used to produce both off-axis coherent emission and on-axis incoherent single-shot spectra. The total coherent infrared power scales inversely with the bunch length and the spectral cutoff is an indication of bunch length. The density of the power spikes in the single-shot visible spectrum may also be used to estimate the bunch length. In the time domain, the linac accelerating sections and a bending magnet are used to implement the RF-zero phasing method, and a subpicosecond streak camera is also installed. The beam measurements with comparisons of these methods are reported.

DUVFEL photoinjector dynamics: measurement and, simulation

The DUVFEL photoinjector consists of a 1.6 cell BNL gun IV with copper cathode, variable pulse length Ti:Sapp laser, and solenoid magnet. The beam dynamics and the electromagnetic fields in the photoinjector have been characterized by producing a short electron beam with very low charge that is used as a field probe. The transverse beam size and divergence are measured as a function of the initial RF phase and the initial spot size and compared with simulations using the code HOMDYN. The electromagnetic fields used in the simulations are produced by SUPERFISH, and have been verified with RF measurements. The simulations and measurements of beam dynamics are presented.

Measured properties of the DUVFEL high brightness, ultrashort electron beam

The DUVFEL electron linac is designed to produce sub-picosecond, high brightness electron bunches to drive an ultraviolet FEL. The accelerator consists of a 1.6 cell S-band photoinjector, variable pulse length Ti:Sapp laser, 4 SLAC-type S-band accelerating sections, and 4-dipole chicane bunch compressor. In preparation for FEL operation, the compressed electron beam has been fully characterized. Measurement of the beam parameters and simulation of the beam are presented.

Optimizing a synchrotron based x-ray lithography system for IC manufacturing

The electron storage ring is a realistic solution as a radiation source for production grade, industrial X-ray lithography system. Today several large scale plans are in motion to design and implement synchrotron storage rings of different types for this purpose in the USA and abroad. Most of the scientific and technological problems related to the physics, design and manufacturing engineering, and commissioning of these systems for microlithography have been resolved or are under extensive study. However, investigation on issues connected to application of Synchrotron Orbit Radiation (SOR ) in chip production environment has been somewhat neglected. In this paper we have filled this gap pointing out direct effects of some basic synchrotron design parameters and associated subsystems (injector, X-ray beam line) on the operation and cost of lithography in production. The following factors were considered: synchrotron configuration, injection energy, beam intensity variability, number of beam lines and wafer exposure concept. A cost model has been worked out and applied to three different X-ray Lithography Source (XLS) systems. The results of these applications are compared and conclusions drawn.

Conceptual design of the NSLS-II injection system

We present the conceptual design of the NSLS-II injection system [1, 2]. The injection system consists of a low-energy linac, booster and transport lines. We review two different injection system configurations; a booster located in the storage ring tunnel and a booster housed in a separate building. We briefly discuss main parameters and layout of the injection system components.

NSLS upgrade concept

To address the growing needs of the NSLS user community we are aggressively pursuing R&D towards a facility upgrade. The present goals are a 3 GeV ultra-low emittance storage ring, tailored to the 5-20 keV photon energy range, that will triple the present NSLS ID capacity, and provide three orders of magnitude increase in brightness over the present brightest NSLS beamlines. To achieve these goals we propose a 24 period TBA lattice, with extensive use of super-conducting small gap undulators. This paper reviews our preliminary design and the key accelerator physics issues.

NSLS II: The Future of the NSLS

The National Synchrotron Light Source at BNL was the first dedicated light source facility and it has now operated for more than 20 years. During this time the user community has grown to more than 2400 users annually. To insure that this vibrant user community has access to the highest quality photon beams, the NSLS is pursuing the design of a new ultra-high brightness (∼1021) electron storage ring, tailored to the 0.3-20 KeV photon energy range. We present our preliminary design and review the critical accelerator physics design issues.

Modeling and measurements of the DUVFEL photoinjector cavity rf properties

The 1.6 cell S-band photoinjector cavity has been in operation at the DUVFEL at BNL for the past year. The initial beam measurements indicated a higher than expected emittance and beam divergence at the exit of the gun field. The imbalance in the two cells was suspected, but lack of field probes in the cavity prohibited direct confirmation. A detailed SUPERFISH model was constructed of the cavity assembly. The field balance as a function of cathode plate and tuner position was determined using the model. A series of calibrated measurements of both the cavity RF properties and the delivered RF power was undertaken. Electron beam properties were also measured as a function of cavity tune. Significant improvements in beam quality were achieved. The simulations and measurements are presented.

BNL Source Development Laboratory

The NSLS has a long-standing interest in providing the best possible synchrotron radiation sources for its user community, and hence, has recently established the Source Development Laboratory (SDL) to pursue research into fourth generation synchrotron radiation sources. A major element of the program includes development of a high peak power FEL meant to operate in the vacuum ultraviolet. The objective of the program is to develop the source, and experimental technology together to provide the greatest impact on UV science. The accelerator under construction for the SDL consists of a high brightness rf photocathode electron gun followed by a 230 MeV short pulse linac incorporating a magnetic chicane for pulse compression. The gun drive laser is a wide bandwidth Ti:sapphire regenerative amplifier capable of pulse shaping which will be used to study non-linear emittance compensation. Using the compressor, 1 nC bunches with a length as small as 50 micrometer sigma (2 kA peak current) are available for experiments. In this paper we briefly describe the facility and detail our plans for utilizing the 10 m long NISUS wiggler to carry out single pass FEL experiments. These include a 1 micrometer SASE demonstration, a seeded beam demonstration at 300 nm, and a high gain harmonic generation experiment at 200 nm. The application of chirped pulse amplification to this type of FEL also is discussed.