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A polarized hydrogen/deuterium internal gas target has been constructed and operated at the internal target region of the South Hall Ring (SHR) of the MIT-Bates Linear Accelerator Center to carry out measurements of spin-dependent electron scattering at 850 MeV. The target used an Atomic Beam Source (ABS) to inject a flux of highly polarized atoms into a thin-walled, coated storage cell. The polarization of the electron beam was determined using a Compton laser backscattering polarimeter. The target polarization was determined using well-known nuclear reactions. The ABS and storage cell were embedded in the Bates Large Acceptance Toroidal Spectrometer (BLAST), which was used to detect scattered particles from the electron–target interactions. The target has been designed to rapidly ( ∼ 8 h ) switch operation from hydrogen to deuterium. Further, this target was the first to be operated inside a magnetic spectrometer in the presence of a magnetic field exceeding 2 kG. An ABS intensity 2.5 × 10 16 at / s and a high polarization ( ≈ 70 % ) inside the storage cell have been achieved. The details of the target design and construction are described here and the performance over an 18 month period is reported.

We report the development and implementation of an energy feedback system for the MIT/Bates Linear Accelerator Center. General requirements of the system are described, as are the specific requirements, features, and components of the system unique to its implementation at the Bates Laboratory. We demonstrate that with the system in operation, energy fluctuations correlated with the 60 Hz line voltage and with drifts of thermal origin are reduced by an order of magnitude.

The extent of penetration of an acidic solution into a melamine-acrylic coating, the bulk changes in the thermal properties of the coating, and the chemistry and kinetics of acid degradation were investigated. Fluorescent microscopy experiments showed that significant penetration of the clearcoat occurs rapidly with acidic solutions. Thermal analysis of a matrix of samples exposed to a variety of conditions showed that significant differences occurred as a function of time, temperature, and acid concentration. Infrared analysis showed unreacted excess alkoxy-methyl melamine was hydrolyzed first, followed by the hydrolysis of the crosslinks.

The ultra-short bunch is the key for producing strong terahertz coherent synchrotron radiation (CSR) and some other applications. A study is being conducted at MIT-Bates South Hall Ring to get 1 mm or shorter electron bunch length. A set of low momentum compaction lattice configurations have been designed. In first beam experiment in 2004, two of these configurations were successfully commissioned in which the momentum compaction was reduced by two orders of magnitude. About 1 mm rms bunch length was measured with a streak camera. It has been demonstrated that this storage ring machine has a great degree of flexibility and potential as an ideal test bed for various advanced beam physics studies.

We investigate the terahertz coherent synchrotron radiation (CSR) potential of the South Hall Ring (SHR) at MIT-Bates Linear Accelerator Center. The SHR is equipped with a unique single cavity, 2.856 GHz RF system. The high RF frequency is advantageous for producing short bunch length and for having higher bunch current threshold to generate stable CSR. Combining with other techniques such as external pulse stacking cavity, femtosecond laser slicing, the potential for generating ultra-stable, high power, broadband terahertz CSR is very attractive. Beam dynamics issues related to short bunch length operation, such as multi-bunch instability (perhaps associated with the high frequency RF system), are considered. The SHR is ideal for experimental exploration of such issues, which could affect bunch length, bunch intensity and beam stability. Results of initial tests of low momentum compaction lattices and bunch length measurements are presented and compared to expectations.

The MIT-Bates South Hall Ring is equipped with a unique 2.856 GHz RF system. High RF frequency is advantageous in generating brilliant stable THz coherent synchrotron radiation (CSR) from an electron storage ring. Intense sub-THz coherent CSR radiation was observed from the (SHR) recently when the ring is operating in a low momentum compaction (a) lattice mode. The signal to background (300 K blackbody) ratio was up to 80000 near 3 cm/sup -1/ frequency. Suppressing beam instabilities and store beam with very short bunch length emerged as the major technical challenges for using such high RF frequency system in storage ring based THz source. Plans to address these issues are presented.

A balanced optical-RF phase detector for the extraction of low-jitter RF-signals from optical pulse trains, which is robust against drifts and photodetector nonlinearities, is presented. Sub-10 fs in-loop relative timing jitter is demonstrated.

In 2003, the installation and commissioning of the Bates Large Acceptance Spectrometer Toroid (BLAST) came in its final state. The South Hall Ring (SHR) commissioning has been dynamically integrated in this process to provide high quality electron beams under BLAST experimental conditions. The design goal of 80 mA stored high polarization beams is met routinely. Results of beam development for the BLAST commissioning runs in 2002 and 2003 are presented. New developments in beam diagnostic and spin manipulation are also presented.

Experiments with a polarized electron beam stored in the South Hall Ring (SHR) at MIT‐Bates Linear Accelerator Center will begin in 2003. Currently, the commissioning of BLAST detector is under way. The polarized injector uses for the first time high power diode array laser for photoemission. The laser operates at a wavelength of 808 nm and produces peak power up to 150 W at a duty factor of 1.5%. Higher power is available at lower duty factor. The laser is coupled to a fiber, laser beam emitting from the fiber has an emittance of 200 mm⋅mrad and a set of lenses is used to deliver the beam through polarizing optics to a strained GaAs crystal inside the electron gun. The photocathode has a diameter of 11 mm and the laser illuminates the entire area. The gun optics has been specifically designed for such a large beam spot size. The diode laser provides an excellent stability and convenience of operation. At the same time, large divergence of the laser beam requires special attention to the transport system ...

The MIT-Bates South Hall Ring has been successfully commissioned for internal target experiments. More than 150 mA of stored beam has been circulated through a 40 cm long 1.5 cm diameter internal target cell. The ring has also been tuned for the first experiment on an external target using a resonantly extracted high duty factor beam. Beam-based measurements of the ring optics by means of analyzing the beam orbit response matrix, and comparing the results with models, have produced much needed information to set up the ring optics. Efforts have been made to improve the measurement precision, and to put the entire process on-line for use during machine operation.

The decay of Te/sup 132/ produced by fission of uranium has been investigated by using a scintillation spectrometer. In addition to the previously reported 0.23-Mev gamma ray and the iodine K x ray, a 0.053-Mev gamma ray has been observed. Coincidence measurements permitted the determination of K- shell conversion coefficients for the two transitions. Probable decay schemes compatible with the observations are discussed. (auth)