[en] We have examined the feasibility of a fusion γ-ray diagnostic for the Compact Ignition Tokamak, which is expected to produce 10²⁰ (d,t) fusion reactions per second. Gamma rays at 16.7 MeV are produced by the t(d,γ)He⁵ fusion reaction. A Monte-Carlo coupled neutron-photon transport code is used to model the expected γ-ray spectrum incident upon a Compton spectrometer backed by a Cerenkov detector. The results indicate that a signal of /approximately/3 x 10⁴cts/s and a signal-to-noise ratio of /approximately/30 can be achieved. 8 refs., 4 figs

[en] Deuterium operation in Alcator C-Mod is expected to produce up to 1 x 10¹⁶ neutrons/s during high performance pulses (1 second duration) with full rf power (6 MW). Neutron production during optimized Ohmic operation should reach 1 x 10¹⁵ neutrons/s. Energy resolved neutron transport calculations have been made for Alcator C-Mod, using both the one-dimensional ANISN code (for deep penetration and activation calculations) and the three dimensional MCNP code (for wall penetrations and near-machine calculations.) The results are used to assess the extent of radiation related health risks imposed by the experiment (anticipated dose rates due to direct radiation exposure, material activation, airborne activity), and then to establish the efficacy of the biological shielding which surrounds the experimental cell. The calculations are used to determine the necessary monitoring and access control for the experiment, and to optimize the design of an igloo structure which will enclose the tokamak. 8 refs., 4 figs., 1 tab

[en] The Fokker-Planck code FPPRF is used to calculate the expected deuterium charge exchange flux along vertical sighlines from TFTR neutral-beam-injected discharges. The feasibility of obtaining central ion temperature measurements by fitting the spectra obtained from these sightlines at two energy regions--above the highest neutral beam injection energy (> 100 keV) and from 20-80 keV--is investigated. It is demonstrated that the central ion temperature can be obtained from the central vertical slightline for fitting the high energy data. The deuterium neutral particle flux energy distribution below the neutral beam injection energy is insentive to the code input ion temperature, however. 6 refs., 12 figs., 1 tab

[en] The ALCATOR C-Mod experiment will be equipped with two PPPL charge exchange neutral particle analyzers (CENAs), one of which views the plasma tangentially (R_tan/R₀=1.05), whereas the second has a horizontally scannable sight line (0≤R_tan/R₀≤0.51). The perpendicularly viewing CENA will be capable of analyzing neutrals up to 600 keV amu for up to three separate species simultaneously. Thus high-energy tails can be observed together with the bulk ion temperature. The operation of both analyzers will allow simultaneous measurements from both the perpendicular and tangential chords. The CENAs will be used to study the effect of ICRF heating on the ion energy distribution with emphasis on the high-energy tail. A Fokker--Planck code (FPPRF) [Hammett, Ph.D. thesis, Princeton (1986)] is used to assess the appropriate operating regime of the analyzer (n≤4x10²⁰ m^-3 for T_i=2 keV, for Maxwellian ion energy distribution). The experimental design and computer simulations will be detailed

[en] This document is designed to address the safety issues involved with the Alcator C-Mod project. This report will begin with a brief description of the experimental objectives which will be followed by information concerning the site. The Alcator C-Mod experiment is a pulsed fusion experiment in which a plasma formed from small amounts of hydrogen or deuterium gas is confined in a magnetic field for short periods (∼1 s). No radioactive fuels or fissile materials are used in the device, so that no criticality hazard exists and no credible nuclear accident can occur. During deuterium operation, the production of a small number of neutrons from a short pulse could result in a small amount of short- and intermediate-lived radioactive isotopes being produced inside the experimental cell. This report will demonstrate that this does not pose an additional hazard to the general population. The health and safety hazards resulting from Alcator C-Mod occur to the workers on the experiment, each of which is described in its own chapter with the steps taken to minimize the risk to employees. These hazards include fire, chemicals and cryogenics, air quality, electrical, electromagnetic radiation, ionizing radiation, and mechanical and natural phenomena. None of these hazards is unique to the facility, and methods of protection from them are well defined and are discussed in the chapter which describes each hazard. The quality assurance program, critical to ensuring the safety aspects of the program, will also be described

[en] Fokker-Planck simulations of the Tokamak Fusion Test Reactor (TFTR) energetic ion mode discharges were performed to evaluate the utility of deriving the central ion temperature, T/sub i/, from deuterium neutral beam charge exchange spectra above the neutral beam injection energy. The T/sub i/ values obtained from fitting the calculated spectra obtained from sightlines nearly tangent to the neutral beam injection radius reproduce the central ion temperature within +-10% over the full range of TFTR energetic ion mode parameters. The code simulations demonstrate that the ion temperature obtained from the high energy tangential deuterium charge exchange spectrum is insensitive to variations in the plasma density, Z/sub eff/, plasma current, loop voltage, and injected neutral beam power and energy. Use of this method to reduce charge exchange data from TFTR energetic ion mode plasmas is demonstrated. 17 refs., 22 figs., 2 tabs

[en] The neutron production rate on Alcator C-Mod is expected to peak at 1x10¹⁶ n/s for the highest performance experimental pulses. Measurement of the total fusion yield is important for both assessing the experiment and for evaluation of radiological data. The neutron detectors must therefore be capable of accurate measurement over a wide operating regime (10¹¹--10¹⁶ n/s from the source). This can be achieved with a series of fission detectors (U²³⁵ and U²³⁸), capable of operating in both a pulsed and current mode. Computer calculations optimizing the placement of these detectors and also the moderator design are detailed. Calibration of this system will be achieved using a Cf ²⁵² source which will be moved on a track continuously around the major axis. It will also be placed discretely at a number of locations in the torus. MCNP calculations will complement the calibration data. Details of the experimental setup and calibration scheme will be presented

[en] Insight into microturbulence and transport in tokamak plasmas is being sought using linear simulations of drift waves near the onset time of an internal transport barrier (ITB) on Alcator C-Mod. Microturbulence is likely generated by instabilities of drift waves and causes transport of heat and particles. This transport is studied because the containment of heat and particles is important for the achievement of practical nuclear fusion. We investigate nearness to marginal stability of ion-temperature-gradient (ITG) modes for conditions in the ITB region at the trigger time for ITB formation. Data from C-Mod, analyzed by TRANSP (a time-dependent transport analysis code), is read by the code TRXPL and made into input files for the parallel gyrokinetic model code GS2. Temperature and density gradients in these input files are modified to produce new input files. Results from these simulations show a weak ITG instability in the barrier region at the time of onset, above marginal stability; the normalized critical temperature gradient is 80% of the experimental temperature gradient. The growth rate increases linearly above the critical value, with the spectrum of ITG modes remaining parabolic up to a multiplicative factor of 2. The effect of varying density gradients is found to be much weaker and causes the fastest growing drift mode to change from ITG to trapped-electron mode character. Simulations were carried out on the NERSC [National Energy Research Supercomputer Center] IBM 6000 SP using 4 nodes, 16 processors per node. Predictive simulations were examined for converged instability after 10,000-50,000 time-steps in each case. Each simulation took approximately 30 minutes to complete on the IBM SP

[en] We have examined the feasibility of a fusion γ-ray diagnostic for the Compact Ignition Tokamak (CIT), which is expected to produce 10²⁰ (d, t) fusion reactions per second. Gamma rays at 16.7 MeV are produced by the t(d, γ)He⁵ fusion reaction. A Monte Carlo coupled neutron--photon transport code is used to model the expected γ-ray spectrum incident upon a Compton spectrometer backed by a Cerenkov detector. The results indicate that a signal of ∼3 x 10⁴ counts/s and a signal-to-noise ratio of ∼30 can be achieved

[en] The challenge of providing an integrated health and safety program for an advanced fusion facility within the university atmosphere is addressed in the Environment, Health ampersand Safety program design for the Alcator C-Mod project at MIT. The hazards common to all fusion experiments such as radiation, cryogenics, high power and voltage, confined spaces, hazardous chemicals, and heavy mechanical and machine equipment must be controlled in an acceptable manner with the coordination of university and facility programs. The development of this program is detailed in this paper