skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: The SSPX Bolometer Systems

Abstract

There are two bolometry systems on SSPX, one that measures the total radiated power and a 16-channel array to measure the radiation profile. The first collimates the radiation through two slits in the horizontal plane spaced a distance s = 1.2 cm apart as in Fig 1. The slit heights are h = 1/100 th of an inch, and the detector material is behind the second one. The number of electrons generated per photon is proportional to the photon energy (except for a factor of 3-4 enhancement in efficiency in the visible) so that the current of electrons is proportional to the power received. The power is in turn the product of the flux hitting the detector material and the projected perpendicular area of the slab material to the line of sight (which is often at an angle to the slab).

Authors:
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (US)
Sponsoring Org.:
USDOE Office of Defense Programs (DP) (US)
OSTI Identifier:
793449
Report Number(s):
UCRL-ID-137802
TRN: US0205238
DOE Contract Number:
W-7405-Eng-48
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Feb 2000
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; BOLOMETERS; EFFICIENCY; ELECTRONS; PHOTONS; RADIATIONS

Citation Formats

Thomassen, K.I. The SSPX Bolometer Systems. United States: N. p., 2000. Web. doi:10.2172/793449.
Copy to clipboard
Thomassen, K.I. The SSPX Bolometer Systems. United States. doi:10.2172/793449.
Copy to clipboard
Thomassen, K.I. Tue . "The SSPX Bolometer Systems". United States. doi:10.2172/793449. https://www.osti.gov/servlets/purl/793449.
Copy to clipboard
@article{osti_793449,
title = {The SSPX Bolometer Systems},
author = {Thomassen, K.I.},
abstractNote = {There are two bolometry systems on SSPX, one that measures the total radiated power and a 16-channel array to measure the radiation profile. The first collimates the radiation through two slits in the horizontal plane spaced a distance s = 1.2 cm apart as in Fig 1. The slit heights are h = 1/100 th of an inch, and the detector material is behind the second one. The number of electrons generated per photon is proportional to the photon energy (except for a factor of 3-4 enhancement in efficiency in the visible) so that the current of electrons is proportional to the power received. The power is in turn the product of the flux hitting the detector material and the projected perpendicular area of the slab material to the line of sight (which is often at an angle to the slab).},
doi = {10.2172/793449},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Feb 01 00:00:00 EST 2000},
month = {Tue Feb 01 00:00:00 EST 2000}
}
Copy to clipboard
Technical Report:
View Technical Report
DOI:  10.2172/793449
Save / Share:
Export Metadata
Save to My Library
You must Sign In or Create an Account in order to save documents to your library.

  • A 3He cryostat which was constructed to cool a germanium bolometer for use as an infrared detector at submillimeter wavelength is discussed. The system had better sensitivity than any other existing system for these wavelengths the system could be improved if better optical coupling could be achieved between the bolometer and the incoming photon stream. Considerable effort was expended to improve this coupling. Even the best results however, fell short of an ideal system by a factor of nearly 5 in coupling efficiency.

  • An analytical approximation to an R-L-C circuit representing SSPX is shown to reproduce the observed capacitor bank efficiency and gun optimization data. As in the SPICE code, the spheromak gun is represented by a fixed resistance chosen to balance energy transfer to the gun. A revised estimate of the magnetic decay time in SSPX Shot 1822 then brings our estimate of the gun efficiency itself in line with the observed spheromak magnetic field for this shot. Prompted by these successes, we present a turbulence-based theoretical model for the spheromak resistance that can be implemented in the SPICE code, of themore » form: R{sub s} = {kappa}I (1-I{sub 0}/I){sup 2} where I is the gun current, I{sub 0} = ({Lambda}{sub 0}/{mu}{sub 0}){Phi} with bias flux and Taylor eigenvalue {lambda}{sub 0}, and {kappa} is a coefficient based on the magnetic turbulence model employed in Dan Hua's spheromak simulation code. The value of {kappa} giving a good energy balance (around 0.1 m{Omega}/KA) implies substantial turbulence levels. Implementing our model in SPICE would provide a calibration for theoretical calculations of the turbulence. Our analytic approximation to the SPICE code provides guidance to optimize future performance in SSPX, the greatest benefit appearing to come from reducing or eliminating the protective resistor to increase bank efficiency. Eliminating the resistor altogether doubles the bank efficiency and the spheromak magnetic energy.« less

  • The Sustained Spheromak Physics Experiment is proposed for experimental studies of spheromak confinement issues in a controlled way: in steady state relative to the confinement timescale and at low collisionality. Experiments in a flux - conserver will provide data on transport in the presence of resistive modes in shear-stabilized systems and establish operating regimes which pave the way for true steady-state experiments with the equilibrium field supplied by external coils. The proposal is based on analysis of past experiments, including the achievement of T{sub e} = 400 eV in a decaying spheromak in CTX. Electrostatic helicity injection from a coaxialmore » ``gun`` into a shaped flux conserver will form and sustain the plasma for several milliseconds. The flux conserver minimizes fluxline intersection with the walls and provides MHD stability. Improvements from previous experiments include modem wall conditioning (especially boronization), a divertor for density and impurity control, and a bias magnetic flux for configurational flexibility. The bias flux will provide innovative experimental opportunities, including testing helicity drive on the large-radius plasma boundary. Diagnostics include Thomson scattering for T{sub e} measurements and ultra-short pulse reflectrometry to measure density and magnetic field profiles and turbulence. We expect to operate at T{sub e} of several hundred eV, allowing improved understanding of energy and current transport due to resistive MHD turbulence during sustained operation. This will provide an exciting advance in spheromak physics and a firm basis for future experiments in the fusion regime.« less

  • ; ;
    A model for spheromak magnetic field buildup and electron thermal transport, including a thermal diffusivity associated with magnetic turbulence during helicity injection is applied to a SSPX equilibrium, with a maximum final magnetic field of 1.3 T. Magnetic field-buildup times of 1.0 X 10-3, 5.0 X 10-4 and 1.0 X 10-4 s were used in the model to examine their effects on electron thermal transport. It is found that at transport run time of 4 x 10-3 s, the fastest buildup-time results in the highest final temperature profile, with a core temperature of 0.93 kev while requiring the lowest inputmore » energy at 140 KJ. The results show that within the model the most rapid buildup rate generates the highest electron temperature at the fastest rate and at the lowest consumption of energy. However, the peak power requirements are large (> 600 MW for the fastest buildup case examined).« less

  • The Sustained Spheromak Physics Experiment (SSPX) shows considerable sensitivity to the value of the injected (''gun'') current, I{sub gun}, parameterized by the relative values of {lambda}{sub gun} = {mu}{sub 0}I{sub gun}/{Psi}{sub gun} (with {Psi}{sub gun} the bias poloidal magnetic flux) to the lowest eigenvalue of {del} x B = {lambda}{sub FC}B in the flux conserver geometry. This report discusses modeling calculations using the NIMROD resistive-MHD code in the SSPX geometry. The behavior is found to be very sensitive to the profile of the safety factor, q, with the excitation of interior MHD modes at low-order resonant surfaces significantly affecting themore » evolution. Their evolution affects the fieldline topology (closed flux, islands, stochastic fieldlines confined by KAM surfaces, and open fieldlines), and thus electron temperature and other parameters. Because of this sensitivity, a major effect is the modification of the q-profile by the current on the open fieldlines in the flux core along the geometric axis. The time-history of a discharge can thus vary considerably for relatively small changes in I{sub gun}. The possibility of using this sensitivity for feedback control of the discharge evolution is discussed, but modeling of the process is left for future work.« less