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The aim of this study was to evaluate whether radiologically defined sarcopenia, or a low skeletal muscle index (SMI), could be used as a practical biomarker for frailty and postoperative complications (POC) in patients with head and neck skin cancer (HNSC). This was a retrospective study on prospectively collected data. The L3 SMI (cm2/m2) was calculated with use of baseline CT or MRI neck scans and low SMIs were defined using sex-specific cut-off values. A geriatric assessment with a broad range of validated tools was performed at baseline. POC was graded with the Clavien–Dindo Classification (with a grade of > II as the cut-off). Univariate and multivariable regression analyses were performed with low SMIs and POC as the endpoints. The patients’ (n = 57) mean age was 77.0 ± 9 years, 68.4% were male, and 50.9% had stage III–IV cancer. Frailty was determined according to Geriatric 8 (G8) score (OR 7.68, 95% CI 1.19–49.66, p = 0.032) and the risk of malnutrition was determined according to the Malnutrition Universal Screening Tool (OR 9.55, 95% CI 1.19–76.94, p = 0.034), and these were independently related to low SMIs. Frailty based on G8 score (OR 5.42, 95% CI 1.25–23.49, p = 0.024) was the only variable related to POC. However, POC was more prevalent in patients with low SMIs (∆ 19%, OR 1.8, 95% CI 0.5–6.0, p = 0.356).To conclude, a low SMI is a practical biomarker for frailty and malnutrition in HNSC. Future research should be focused on interventions based on low SMI scores and assess the effect of the intervention on SMI, frailty, malnutrition, and POC.

Objectives Cross-sectional area (CSA) measurements of the neck musculature at the level of third cervical vertebra (C3) on CT scans are used to diagnose radiological sarcopenia, which is related to multiple adverse outcomes in head and neck cancer (HNC) patients. Alternatively, these assessments are performed with neck MRI, which has not been validated so far. For that, the objective was to evaluate whether skeletal muscle mass and sarcopenia can be assessed on neck MRI scans. Methods HNC patients were included between November 2014 and November 2018 from a prospective data-biobank. CSAs of the neck musculature at the C3 level were measured on CT (n = 125) and MRI neck scans (n = 92 on 1.5-T, n = 33 on 3-T). Measurements were converted into skeletal muscle index (SMI), and sarcopenia was defined (SMI 2/m2). Pearson correlation coefficients, Bland–Altman plots, McNemar test, Cohen’s kappa coefficients, and interclass correlation coefficients (ICCs) were estimated. Results CT and MRI correlated highly on CSA and SMI (r = 0.958–0.998, p 2/m2). There was no significant difference between CT and MRI in diagnosing sarcopenia (McNemar, p = 0.5–1.0). Agreement on sarcopenia diagnosis was good with κ = 0.956–0.978 and κ = 0.870–0.933, for 1.5-T and 3-T respectively. Observer ICCs in MRI were excellent. In general, T2-weighted images had the best correlation and agreement with CT. Conclusions Skeletal muscle mass and sarcopenia can interchangeably be assessed on CT and 1.5-T and 3-T MRI neck scans. This allows future clinical outcome assessment during treatment irrespective of used modality. Key Points • Screening for low amount of skeletal muscle mass is usually measured on neck CT scans and is highly clinical relevant as it is related to multiple adverse outcomes in head and neck cancer patients. • We found that skeletal muscle mass and sarcopenia determined on CT and 1.5-T and 3-T MRI neck scans at the C3 level can be used interchangeably. • When CT imaging of the neck is missing for skeletal muscle mass analysis, patients can be assessed with 1.5-T or 3-T neck MRIs.

A low skeletal muscle index (SMI), defined with cut-off values, is a promising predictor for adverse events (AEs) in head and neck squamous cell cancer (HNSCC) patients. The aim was to generate sex-specific SMI cut-off values based on AE to diagnose low SMI and to analyse the relationship between low SMI and AEs in HNSCC patients. In this present study, HNSCC patients were prospectively included in a large oncological data-biobank and SMI was retrospectively measured using baseline neck scans. In total, 193 patients were included and were stratified according to treatment modality: (chemo-)radiotherapy ((C)RT) (n = 135) and surgery (n = 61). AE endpoints were based on the occurrence of clinically relevant toxicities (Common Terminology Criteria for Adverse Events grade ≥ III) and postoperative complications (Clavien–Dindo Classification grade ≥ II). Sex-specific SMI cut-off values were generated with receiver operating characteristic curves, based on the AE endpoints. The relationship of the baseline characteristics and AEs was analysed with logistic regression analysis, with AEs as the endpoint. Multivariable logistic analysis showed that low SMI (OR 3.33, 95%CI 1.41–7.85) and tumour stage (OR 3.45, 95%CI 1.28–9.29) were significantly and independently associated to (C)RT toxicity. Low SMI was not related to postoperative complications. To conclude, sex-specific SMI cut-off values, were generated based on the occurrence of AEs. Low SMI and tumour stage were independently related to (C)RT toxicity in HNSCC patients.

We report the measurement of the beam-vector and tensor asymmetries A_{ed}^{V} and A_{d}^{T} in quasielastic (e[over →],e^{'}p) electrodisintegration of the deuteron at the MIT-Bates Linear Accelerator Center up to missing momentum of 500 MeV/c. Data were collected simultaneously over a momentum transfer range 0.1

We report the measurement of the beam-vector and tensor asymmetries A_{ed}^{V} and A_{d}^{T} in quasielastic (e[over →],e^{'}p) electrodisintegration of the deuteron at the MIT-Bates Linear Accelerator Center up to missing momentum of 500 MeV/c. Data were collected simultaneously over a momentum transfer range 0.1Q^{2}0.5 (GeV/c)^{2} with the Bates Large Acceptance Spectrometer Toroid using an internal deuterium gas target polarized sequentially in both vector and tensor states. The data are compared with calculations. The beam-vector asymmetry A_{ed}^{V} is found to be directly sensitive to the D-wave component of the deuteron and has a zero crossing at a missing momentum of about 320 MeV/c, as predicted. The tensor asymmetry A_{d}^{T} at large missing momentum is found to be dominated by the influence of the tensor force in the neutron-proton final-state interaction. The new data provide a strong constraint on theoretical models.

The Bates large acceptance spectrometer toroid (BLAST) experiment was operated at the MIT-Bates Linear Accelerator Center from 2003 until 2005. The detector and experimental program were designed to study, in a systematic manner, the spin-dependent electromagnetic interaction in few-nucleon systems. As such the data will provide improved measurements for neutron, proton, and deuteron form factors. The data will also allow details of the reaction mechanism, such as the role of final state interactions, pion production, and resonances to be studied. The experiment used: a longitudinally polarized electron beam stored in the South Hall Storage Ring; a highly polarized, isotopically pure, internal gas target of hydrogen or deuterium provided by an atomic beam source: and a symmetric, general purpose detector based on a toroidal spectrometer with tracking. time-of-flight, Cherenkov, and neutron detectors. Details of the experiment and operation are presented. (C) 2009 Elsevier B.V. All rights reserved.

The polarized electron source at MIT-Bates has been developed to provide beams for nuclear physics experiments with a very diverse set of requirements. The source has combined operation at high peak and average current with high polarization. Developments have included the pioneering of several techniques used in parity violating experiments to remove helicity correlations from beam properties. This paper describes the design of the source and its performance during beam operations.

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.

Accurate measurements of the p(e,e?p)pi0 reaction were performed at Q^2=0.127(GeV/c)^2 in the Delta resonance energy region. The experiments at the MIT-Bates Linear Accelerator used an 820 MeV polarized electron beam with the out of plane magnetic spectrometer system (OOPS). In this paper we report the first simultaneous determination of both the TL and TL? (``fifth" or polarized) cross sections at low Q^{2} where the pion cloud contribution dominates the quadrupole amplitudes (E2 and C2). The real and imaginary parts of the transverse-longitudinal cross section provide both a sensitive determination of the Coulomb quadrupole amplitude and a test of reaction calculations. Comparisons with model calculations are presented. The empirical MAID calculation gives the best overall agreement with this accurate data. The parameters of this model for the values of the resonant multipoles are |M_{1+}(I=3/2)|= (40.9 \pm 0.3)10^{-3}/m_pi, CMR= C2/M1= -6.5 \pm 0.3%, EMR=E2/M1=-2.2 \pm 0.9%, where the errors are due to the experimental uncertainties.

We report on the design and performance of compact detector packages currently installed in the four magnetic out-of-plane spectrometers for electron scattering experiments at the MIT-Bates Linear Accelerator Center. The detector packages have been designed to meet the mechanical requirements arising from out-of-plane particle detection. They offer good trajectory and momentum reconstruction, particle identification and time-of-flight measurements for electrons, pions, protons, and deuterons with large momentum bites and in broad kinematical ranges and high luminosities. The detectors have so far been used with great success in out-of-plane measurements of 12 C ( e → , e ′ p ) , 2 H ( e → , e ′ p ) , virtual Compton scattering below pion threshold and in studies of the N → Δ transition in both exclusive reaction channels 1 H ( e → , e ′ p ) π 0 and 1 H ( e → , e ′ π + )n .

An accurate calibration of the MIT-Bates electron beam energy has been achieved. The electron beam was injected into the MIT-Bates South Hall Ring and the spin-precession frequency, Ω s , was measured. From the spin-precession frequency the equilibrium energy of the ring was determined to be 370.3115±0.0021±0.0004 MeV, where the first error is statistical and the second is systematic. The energy of the beam delivered by the linac was determined to be 369.954±0.023±0.300 MeV. This provides a rigorous check on the accuracy of the facility's energy analyzing magnets. The first moment of the energy distribution was also measured. By observing the time constant of the spin diffusion with zero power in the South Hall Ring RF cavity, we obtained a value of σ γ γ = (3.7±0.5) × 10 −4 . We provide a lower limit to the polarization lifetime. At a beam energy of 370 MeV no measurable decrease in the polarization was observed up to 2 ms after injection.

We report a precision measurement of the deuteron tensor analyzing powers ${T}_{20}$ and ${T}_{21}$ at the MIT-Bates Linear Accelerator Center. Data were collected simultaneously over a momentum transfer range $Q=2.15--4.50\text{ }\text{ }{\mathrm{fm}}^{\ensuremath{-}1}$ with the Bates Large Acceptance Spectrometer Toroid using a highly polarized deuterium internal gas target. The data are in excellent agreement with calculations in a framework of effective field theory. The deuteron charge monopole and quadrupole form factors ${G}_{C}$ and ${G}_{Q}$ were separated with improved precision, and the location of the first node of ${G}_{C}$ was confirmed at $Q=4.19\ifmmode\pm\else\textpm\fi{}0.05\text{ }\text{ }{\mathrm{fm}}^{\ensuremath{-}1}$. The new data provide a strong constraint on theoretical models in a momentum transfer range covering the minimum of ${T}_{20}$ and the first node of ${G}_{C}$.

We report precision {sup 1}H(e, e{sup '{pi}+})n measurements in the {Delta}(1232) resonance at Q{sup 2}=0.127(GeV/c){sup 2} obtained at the MIT-Bates out-of-plane scattering facility. These are the lowest, but nonzero, Q{sup 2} measurements in the {pi}{sup +} channel. The data offer tests of the theoretical calculations, particularly of the background amplitude contributions. The chiral effective field theory and Sato-Lee model calculations are not in agreement with this experiment.

The roles played by mesons in the electromagnetic form factors of the nucleon are explored using as a basis a model containing vector mesons with coupling to the continuum together with the asymptotic $Q^2$ behavior of perturbative QCD. Specifically, the vector dominance model (GKex) developed by Lomon is employed, as it is known to be very successful in representing the existing high-quality data published to date. An analysis is made of the experimental uncertainties present when the differences between the GKex model and the data are expanded in orthonormal basis functions. A main motivation for the present study is to provide insight into how the various ingredients in this model yield the measured behavior, including discussions of when dipole form factors are to be expected or not, of which mesons are the major contributors, for instance, at low-$Q^2$ or large distances, and of what effects are predicted from coupling to the continuum. Such insights are first discussed in momentum space, followed by an analysis of how different and potentially useful information emerges when both the experimental and theoretical electric form factors are Fourier transformed to coordinate space. While these Fourier transforms should not be interpreted as "charge distributions", nevertheless the roles played by the various mesons, especially which are dominant at large or small distance scales, can be explored via such experiment--theory comparisons., Resubmitted to PRC

We report new measurements of the neutron charge form factor at low momentum transfer using quasielastic electrodisintegration of the deuteron. Longitudinally polarized electrons at an energy of 850 MeV were scattered from an isotopically pure, highly polarized deuterium gas target. The scattered electrons and coincident neutrons were measured by the Bates Large Acceptance Spectrometer Toroid (BLAST) detector. The neutron form factor ratio ${G}_{E}^{n}/{G}_{M}^{n}$ was extracted from the beam-target vector asymmetry ${A}_{\mathrm{ed}}^{V}$ at four-momentum transfers ${Q}^{2}=0.14$, 0.20, 0.29, and $0.42\text{ }\text{ }(\mathrm{GeV}/c{)}^{2}$.

We report new measurements of the neutron charge form factor at low momentum transfer using quasielastic electrodisintegration of the deuteron. Longitudinally polarized electrons at an energy of 850 MeV were scattered from an isotopically pure, highly polarized deuterium gas target. The scattered electrons and coincident neutrons were measured by the Bates Large Acceptance Spectrometer Toroid (BLAST) detector. The neutron form factor ratio GEn/GMn was extracted from the beam-target vector asymmetry AedV at four-momentum transfers Q2=0.14, 0.20, 0.29, and 0.42 (GeV/c)2.

We report the first precision measurement of the proton electric to magnetic form factor ratio from spin-dependent elastic scattering of longitudinally polarized electrons from a polarized hydrogen internal gas target. The measurement was performed at the MIT-Bates South Hall Ring over a range of four-momentum transfer squared Q2 from 0.15 to 0.65 (GeV/c)(2). Significantly improved results on the proton electric and magnetic form factors are obtained in combination with existing cross-section data on elastic electron-proton scattering in the same Q2 region.

The mean square polarizability radii of the proton have been measured for the first time in a virtual-Compton-scattering experiment performed at the MIT-Bates out-of-plane scattering facility. Response functions and polarizabilities obtained from a dispersion analysis of the data at Q2 = 0.057 GeV2/c2 are in agreement with O(p3) heavy baryon chiral perturbation theory. The data support the dominance of mesonic effects in the polarizabilities.

The lepton ring of eRHIC is being designed to provide intense, highly polarized electron and positron beams at 5-10 GeV energy range for the high luminosity lepton-hadron collisions. In this paper the estimates of major beam instabilities in the lepton storage ring are presented. Besides conventional impedance-driven instablities the fast beam-ion instability and electron cloud effects are major concerns. The studies suggest that those instbilities would not limit the performance of the lepton ring of eRHIC.

The x-ray FEL at MIT[1] is one example of a design for a new generation linac-based light source. Such a new machine requires very high quality electron beams. Besides the usual requirements on beam parameters such as emittance, energy spread, peak current, there are new challenges emerging in the design studies, e.g., the arrival timing of electron beam must reach precision below tens of femtoseconds level to ensure the laser seed overlaps the desired sections of electron bunch in the multiple-stage HGHG process. In this paper we report the progress on design optimization towards high quality and low sensitivity beams.

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.

We present the design, simulations and measurements of a prototype passive RF cavity for a polarimeter with a transversely polarized electron beam interacting with the longitudinal gradient of the transverse component of magnetic field in the TE011 mode of the cavity. Magnetic coupling of a polarized electron beam at the Bates accelerator may produce signals of the order of a microwatt, permitting fast and accurate polarization measurement.

We report new precise H$(e,e^\prime p)\pi^0$ measurements at the $\Delta(1232)$ resonance at $Q^2= 0.127$ (GeV/c)$^2$ using the MIT/Bates out-of-plane scattering (OOPS) facility. The data reported here are particularly sensitive to the transverse electric amplitude ($E2$) of the $\gamma^* N\to\Delta$ transition. Analyzed together with previous data yield precise quadrupole to dipole amplitude ratios $EMR = (-2.3 \pm 0.3_{stat+sys} \pm 0.6_{model})%$ and $CMR = (-6.1 \pm 0.2_{stat+sys}\pm 0.5_{model})%$ and for $M^{3/2}_{1+} = (41.4 \pm 0.3_{stat+sys}\pm 0.4_{model})(10^{-3}/m_{\pi^+})$. They give credence to the conjecture of deformation in hadronic systems favoring, at low $Q^2$, the dominance of mesonic effects., Comment: 4 pages, 1figure

A multiple cell 1.3 GHz room-temperature photoinjector is under design for the MIT Bates X-ray laser project. The design features include tunable intercavity phase shifts allowing separate phasing of the cells for velocity bunching of the beam in the following drift, and optimization of cell shape for high shunt impedance and low wall power density. Beam dynamics are studied for charges ranging from 0.1 to 1 nC using a model, non-ideal laser profile shape. It is shown that collective effects at the high end of the range cause loss of beam brightness.

MIT and the Bates Linear Accelerator Center are exploring the construction of an X-ray free electron laser user facility. It will be based on a superconducting linac of approximately 4 GeV energy, and produce XUV light in the 0.3–100 nm wavelength range at kilohertz repetition rates. The facility will be a full user facility incorporating multiple beamlines. Conventional lasers that produce the electron beam, seed the FEL, and execute pump–probe experiments are carefully integrated. The current design of the facility is discussed.

The performance of an X-ray free electron laser can be substantially enhanced if a coherent seed source is used to provide sufficient initial power that it dominates the spontaneous emission in the early part of the undulator. The FEL output then becomes an amplified reproduction of the input seed having, under certain conditions, the same pulse length and bandwidth. For studies of molecular and atomic time dynamics the pulse length may be very short, reaching below 1 fs with a transform limited bandwidth of a few tenths of a percent. For spectroscopy and diffraction experiments the beam may alternatively be made monochromatic at the level of one part in 10/sup 5/ or better, with a pulse length of tens of femtoseconds. Simulation studies of seeded FEL performance at 0.3 nm using the code GINGER are presented.

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.

During the fall of 2001, the polarized source at MIT delivered over 140 Coulombs of high quality polarized beams to the SAMPLE‐III 125 MeV parity violating experiment. Prior to the experiment, the source was reconfigured to deliver highly polarized beam using the new high power diode array laser system with large aperture beam optics, and a strained layer GaAsP photocathode from St. Petersburg. The results of these tests will be presented. The production run for SAMPLE‐III was then carried out with a bulk GaAs and the Ar‐Ti:Sapphire laser system. Since April of this year, the source has been delivering high polarization beams to the South Hall Ring for commissioning of the BLAST spectrometer. The stored current in the ring exceeds 100 mA. This is accomplished using the high power diode laser system and high‐gradient‐doped strained GaAsP photocathodes from Bandwidth Semiconductor Inc. tuned for 810 nm. The operational lifetime of the photocathode is excellent. A status report of the Bates polarized source ...

The MIT‐Bates Compton Polarimeter, a laser back‐scattering device, is used to measure the polarization of electron beams circulating in the South Hall Ring for a range of energies between 300 and 1000 MeV. The apparatus is described in detail and compared to other polarimeters operating within a similar energy region. Preliminary polarization results at 850 MeV are presented.

In 1998–2001 three series of SAMPLE experiment [1–3] were conducted at the MIT‐Bates Linear Accelerator Center. SAMPLE measures parity‐violating effects in electron scattering from protons and deuterons. The measured asymmetry associated with electron helicity is very small (about 1 ppm). In order to reduce systematic errors, the properties of the beam (intensity, position, size and energy) must remain unchanged when the helicity of polarized electrons is reversed. In this paper we analyze the sources of the helicity‐correlated effects in the electron beam and our approach to minimize them.

The polarization dependence of Compton scattering in magnetized iron can be used to determine the polarization of an incident photon beam. This can in turn be related to the polarization of the electron beam which radiated the photons. It is difficult to calculate the analyzing power of these devices absolutely, however they are of great utility for rapid, relative measurements of electron beam polarization. These devices have been used at Bates as relative electron polarization monitors at 20 and 200 MeV. Efforts are now being made to use the device at 850 MeV as an online measure of the beam polarization in the South Hall Ring. A technique to calibrate these devices and build an affordable, absolute polarimeter is also being explored.

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 ...

We report a new determination of the strange quark contribution to the proton's magnetic form factor at a four-momentum transfer Q2 = 0.1 (GeV/c)^2 from parity-violating e-p elastic scattering. The result uses a revised analysis of data from the SAMPLE experiment which was carried out at the MIT-Bates Laboratory. The data are combined with a calculation of the proton's axial form factor GAe to determine the strange form factor GMs(Q2=0.1)=0.37 +- 0.20 +- 0.26 +- 0.07. The extrapolation of GMs to its Q2=0 limit and comparison with calculations is also discussed., Comment: 6 pages, 1 figure, submitted to Phys. Lett. B

Experimental requirements at Bates place stringent excursion limits on some beam parameters and on measurements of beam properties such as position and charge. Steering elements and measuring devices may be affected by vibrations transmitted along the beam pipe from vacuum pumps and turbulent cooling water flows. A vibration measurement setup, capable of generating displacement spectra and detecting displacements of less than 100 nm at 20 Hz, has been used in detecting and correcting vibration induced beam parameter deterioration and measurement error. The measurement setup, plans for improvements and vibration monitoring on site are described.

The South Hall Ring at the MIT-Bates Linear Accelerator Center is a combination of pulse stretcher ring to produce high duty factor extracted beams and storage ring for use with internal targets. It is designed to operate at energies from 300 MeV to 1 GeV for nuclear physics experiments. In pulse stretching mode, half-integer resonant extraction is used to convert the

An optical design for a spin rotator for the MIT-Bates South Hall Ring is presented. This design maintains longitudinally polarized electrons at both internal and external targets.

The South Hall Ring at the MIT-Bates Linear Accelerator Center is a 1 GeV electron ring for nuclear physics experiments. It is designed to operate in two modes: as a pulse stretcher to deliver high duty factor beams to external targets, and as a storage ring for internal target experiments. To date we have injected beam into the ring using one and two-turn injection, stored beam with a lifetime of several minutes, and achieved early results performing half-integer resonant extraction from the ring in pulse stretcher mode. Experience in commissioning the ring is presented. Future plans for extraction, improved storage and backgrounds, and spin control and measurement in the ring, are also discussed.

This report presents preliminary results of the feasibility study for a polarized electron-proton beam collider with a center of mass energy range of 15-30 GeV.

Measurements of the (2)H((-->)e,e(')p)n reaction were performed with the out-of-plane magnetic spectrometers (OOPS) at the MIT-Bates Linear Accelerator. The longitudinal-transverse, f(LT) and f(')(LT), and the transverse-transverse, f(TT), interference responses at a missing momentum of 210 MeV/c were simultaneously extracted in the dip region at Q2 = 0.15 (GeV/c)(2). In comparison to models of deuteron electrodisintegration, the data clearly reveal strong effects of relativity and final-state interactions and the importance of two-body meson-exchange currents and isobar configurations. We demonstrate that such effects can be disentangled by extracting these responses using the novel out-of-plane technique.

We recently used a prototype rf dipole magnet to study the spin flipping of a 669 MeV horizontally polarized electron beam stored in the presence of a nearly full Siberian snake in the new MIT-Bates storage ring. We flipped the spin by ramping the rf dipole's frequency through an rf-induced depolarizing resonance. After optimizing the frequency ramp parameters, we used multiple spin flipping to measure a spin-flip efficiency of $94.5\ifmmode\pm\else\textpm\fi{}2.5%$. The spin-flip efficiency was apparently limited by the field strength in the air-core prototype rf dipole magnet. This unexpectedly high efficiency indicates that very efficient spin flipping of the ring's stored polarized electron beam should be possible using the much stronger ferrite spin flipper, which is now being built by the University of Michigan's Spin Physics Center.