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Introduction to magnetic confinement fusion diagnostics

Description: These notes present a brief survey of some of the current diagnostic techniques used in magnetic fusion plasma devices. To give an idea of the range of parameters and geometries encountered the parameters of four representative experiments - PLT, TMX, ZT-40 and EBT-I(S) - are given. The central issue of all experiments is to understand the flow of power which can be summarized by two volume integrated equations for the ions and electrons.
Date: June 6, 1980
Creator: Turner, W.C.
Partner: UNT Libraries Government Documents Department

Beam injection in the TMX-U central cell

Description: Results pertaining to the recently modified beam-injection arrangement in the central cell of TMX-U are presented here. These modifications followed our observation that beam atoms injected perpendicular to the magnetic axis between the first two magnet-coil gaps give rise to trapped ions with midplane pitch angles lying in the intervals 68/sup 0/ < theta < 78/sup 0/ and 59/sup 0/ < theta < 65/sup 0/. These pitch-angle intervals are similar in value to the earlier arrangement of beams injected at the midplane at pitch angles of 58 and 70/sup 0/. Normal injection at an off-midplane position has two advantages when compared with off-normal injection at the midplane. First, the unattenuated beam can be dumped in the first-injector region rather than in the plasma region. Second, the beams can be oriented with their long dimension horizontal rather than vertical. The first point al
Date: June 15, 1984
Creator: Turner, W.C.
Partner: UNT Libraries Government Documents Department

Low-energy neutral-beam injection in the central cell of TMX-U

Description: The purpose is to estimate the central-cell parameters that can be reached by injection of low-energy neutral beams. The main advantages of low energy (2-keV full-energy component) over high energy (15-keV full-energy component) are the following: (1) creation of a beam-fueled, potentially confined, central-cell plasma (n approx. = 10/sup 13/ cm/sup -3/, E/sub ic/ approx. = 1 keV, T/sub ec/ approx. = 0.4 keV) without the use of cold-gas injection or ICRH heating; and (2) reduced shielding requirement against neutrals external to the plasma. The reasons for these expectations are the larger ionization cross section and plasma radius (normalized to ion gyroradius) for low-energy compared to high-energy beams.
Date: September 24, 1984
Creator: Turner, W.C.
Partner: UNT Libraries Government Documents Department

Low energy neutral source for fueling the central cell core plasma of TMX-U

Description: The performance of a low energy neutral source formed by negatively biased plates inserted in the edge plasma of the central cell of the Tandem Mirror Experiment-Upgrade (TMX-U) is described. This technique promises to be capable of fueling the high density thermal barrier plasmas. We have found that annular ring electrodes mounted on the sides of the central cell gas box and inclined 45/sup 0/ to the plasma axis can produce about 80 A of inward-directed D/sup 0/ with an average energy E/sub 0/ approx. = 250 eV (where the plate bias = -400 V). This example was calculated for a peak plasma density n/sub e/(0) = 10/sup 13/ cm/sup -3/ and an edge plasma density n/sub L/ = 10/sup 12/ cm/sup -3/ at the limiter edge defined by the biased plates. The energetic neutrals, attenuated by about an e-fold in reaching the plasma center, are thus much more efficient in fueling the core plasma than Frank-Condon atoms, which are attenuated by greater than a factor of 100. In addition, because their energy is greater than Frank-Condon atoms their initial collisional trapping rate in the thermal barrier is reduced by a factor of approximately (100)/sup 3/2/ = 1000.
Date: April 23, 1984
Creator: Turner, W.C.
Partner: UNT Libraries Government Documents Department

Energy Management Curriculum Starter Kit

Description: The Energy Management Curriculum Starter Kit was designed to help engineering educators develop and teach energy management courses. Montana State University and Oklahoma State University courses are embodied in the model curriculum given. The curricula offered at many other universities throughout the United States are also presented. The kit was designed specifically to train engineering students to be good energy managers. Courses at both the undergraduate and postgraduate level are presented.
Date: February 1, 1987
Creator: Turner, W.C.
Partner: UNT Libraries Government Documents Department

Electrostatic ion cyclotron waves and ion energy diffusion in a mirror machine. [2XIIb machine]

Description: Measurements of ion cyclotron fluctuations and ion energy diffusion in the neutral beam injected 2XIIB mirror machine are presented. A narrow band single mode spectrum is always observed. When the plasma is de-stabilized by turning off axially injected streaming plasma, the wave amplitude increases and a simultaneous increase in ion-energy diffusion is observed. The spectral properties of the wave do not change. The data are in accord with a wave particle saturation of the drift cyclotron loss cone (DCLC) mode.
Date: August 1, 1977
Creator: Turner, W. C.
Partner: UNT Libraries Government Documents Department

An induction Linac approach to phase rotation of a muon bunch in the production region of {mu}{sup +}-{mu}{sup {minus}} colliders

Description: The possibility of using an induction linac for phase rotation, or equivalently flattening the head to tail mean energy sweep, of a muon bunch in the production region of a {mu}{sup +} {minus} {mu}{sup {minus}} is examined. Axial spreading of an accelerating bunch is analyzed and the form of appropriate induction cell voltage waveforms is derived. A set of parametric equations for the induction accelerator structure is given and specific solutions are presented which demonstrate the technological feasibility of the induction linac approach to phase rotation.
Date: November 22, 1995
Creator: Turner, W.C.
Partner: UNT Libraries Government Documents Department

Beam tube vacuum in low field and high field very large hadron colliders

Description: Bounds on the beam tube gas pressure and the required pumping speed are estimated for {approximately} 2 T low field (LF) and - 12 T high field (HF) 100 TeV center-of-mass hadron colliders. In both cases photodesorption by synchrotron radiation is the dominant source of gas. Assuming beam-gas scattering limited luminosity lifetime five times the IP scattering lifetime, the required CO equivalent beam tube pressure is 0.25 ntorr for LF and 1.8 ntorr for HF, ambient room temperature equivalent. The CO equivalent pumping speeds required to achieve this pressure within a reasonable beam conditioning time (a few tenths of an operational year at design intensity) are estimated to be {approximately} 300 I/s-m for LF and - 40 I/s-m for HF. For the LF case with a superferric warm and a distributed NEG plus lumped ion or cryo pump system is considered. The size of antechamber needed, ID- 6 cm, requires that it be located outside the - 2 cm C-coil magnet gap. Lumped pumps for pumping CH{sub 4} need to be spaced at - 20 in intervals on the antechamber. For the HF case the likely beam tube temperature .is 15-20 K and cryopumping with a beam screen system is considered. The necessary pumping speed can be achieved with slots covering {approximately} 2 per cent of the beam screen surface.
Date: October 1, 1996
Creator: Turner, W.C.
Partner: UNT Libraries Government Documents Department

Beam tube vacuum in 100 TeV hadron colliders

Description: Bounds on the beam tube gas pressure and the required pumping speed are estimated for {approximately} 2 T low field (LF) and {approximately} 12 T high field (HF) 100 TeV center-of-mass hadron colliders. In both cases photodesorption by synchrotron radiation is the dominant source of gas. Assuming beam-gas scattering limited luminosity lifetime five times the IP scattering lifetime, the required CO equivalent beam tube pressure is 0.25 nTorr for LF and 1.8 nTorr for HF, ambient room temperature equivalent. The CO equivalent pumping speeds required to achieve this pressure within a reasonable beam conditioning time (a few tenths of an operational year at design intensity) are estimated to be {approximately} 300 l/s-m for LF and {approximately} 40 l/s-m for HF. For the LF case with a superferric warm iron magnet, the beam tube is at ambient room temperature and a distributed NEG plus lumped ion or cryo pump system is considered. The size of antechamber needed, ID {approximately} 6 cm, requires that it be located outside the {approximately} 2 cm C-coil magnet gap. Lumped pumps for pumping CH{sub 4} need to be spaced at {approximately} 20 m intervals on the antechamber. For the HF case the likely beam tube temperature is 15--20 K and cryopumping with a beam screen system is considered. The necessary pumping speed can be achieved with slots covering {approximately} 2% of the beam screen surface.
Date: April 1, 1997
Creator: Turner, W.C.
Partner: UNT Libraries Government Documents Department

Laser-plasma interaction experiments at laser wavelengths of 1. 064. mu. m, 0. 532. mu. m and 0. 355. mu. m

Description: Experiments at all three wavelengths included the following: target absorption, stimulated Brillouin scattering, suprathermal electron production, observation of harmonic and half harmonic emission from the plasma as a signature of parametric processes such as 2..omega../sub pe/ and simulated Raman scattering. These experiments are presented and compared with detailed hydro code and plasma simulation results.
Date: January 1, 1982
Creator: Campbell, E.M.; Mead, W.C. & Turner, W.C.
Partner: UNT Libraries Government Documents Department

Tandem mirror and field-reversed mirror experiments

Description: This paper is largely devoted to tandem mirror and field-reversed mirror experiments at the Lawrence Livermore Laboratory (LLL), and briefly summarizes results of experiments in which field-reversal has been achieved. In the tandem experiment, high-energy, high-density plasmas (nearly identical to 2XIIB plasmas) are located at each end of a solenoid where plasma ions are electrostatically confined by the high positive poentials arising in the end plug plasma. End plug ions are magnetically confined, and electrons are electrostatically confined by the overall positive potential of the system. The field-reversed mirror reactor consists of several small field-reversed mirror plasmas linked together for economic reasons. In the LLL Beta II experiment, generation of a field-reversed plasma ring will be investigated using a high-energy plasma gun with a transverse radial magnetic field. This plasma will be further heated and sustained by injection of intense, high-energy neutral beams.
Date: August 21, 1979
Creator: Coensgen, F.H.; Simonen, T.C. & Turner, W.C.
Partner: UNT Libraries Government Documents Department

Ion Desorption Stability in Superconducting High Energy Physics Proton Colliders

Description: In this paper we extend our previous analysis of cold beam tube vacuum in a superconducting proton collider to include ion desorption in addition to thermal desorption and synchrotron radiation induced photodesorption. The new ion desorption terms introduce the possibility of vacuum instability. This is similar to the classical room temperature case but now modified by the inclusion of ion desorption coefficients for cryosorbed (physisorbed) molecules which can greatly exceed the coefficients for tightly bound molecules. The sojourn time concept for physisorbed H{sub 2} is generalized to include photodesorption and ion desorption as well as the usually considered thermal desorption. The ion desorption rate is density dependent and divergent so at the onset of instability the sojourn time goes to zero. Experimental data are used to evaluate the H{sub 2} sojourn time for the conditions of the Large Hadron Collider (LHC) and the situation is found to be stable. The sojourn time is dominated by photodesorption for surface density s(H{sub 2}) less than a monolayer and by thermal deposition for s(H{sub 2}) greater than a monolayer. For a few percent of a monolayer, characteristic of a beam screen, the photodesorption rate exceeds ion desorption rate by more than two orders of magnitude. The photodesorption rate corresponds to a sojourn time of approximately 100 sec. The paper next turns to the evaluation of stability margins and inclusion of gases heavier than H{sub 2} (CO, CO{sub 2} and CH{sub 4}), where ion desorption introduces coupling between molecular species. Stability conditions are worked out for a simple cold beam tube, a cold beam tube pumped from the ends and a cold beam tube with a co-axial perforated beam screen. In each case a simple inequality for stability of a single component is replaced by a determinant that must be greater than zero for ...
Date: May 29, 1995
Creator: Turner, W.C.
Partner: UNT Libraries Government Documents Department

Instrumentation for the absorbers in the low Beta* Insertions of the LHC

Description: Concepts are examined for the measurement of luminosity, beam-beam separation and transverse beam shape and size using the high flux of forward neutral particles produced at the low {beta}* (high luminosity) interaction points (IP's) of the LHC. At design luminosity 10{sup 34} cm{sup -2}sec{sup -1} the flux of neutrals striking the neutral beam absorbers (TAN) in front of the D2 beam separation dipoles is high enough ({approx} 8 neutrons per bunch crossing with mean energy 2.3 TeV) to allow measurement of luminosity with 1% precision in {approx} 1.8 x 10{sup 3} bunch crossings and measurement of beam-beam separation at the collision point with 0.1{sigma}* precision in {approx} 3 x 10{sup 4} bunch crossings. An Argon ionization chamber placed near the shower maximum {approx} 22 cm inside the Cu neutral beam absorber is analyzed as a possible detector. Background effects due to beam-gas interactions, beam-halo scraping, beam crossing angle modulation and transverse drift of the IP are estimated and found to be small compared to the anticipated signals. Extending these concepts to the front quadrupole absorber (TAS) and segmenting the ionization chambers into four quadrants allows additional measurements of the beam-beam crossing angle and the transverse position of the IP.
Date: August 1, 1998
Creator: Turner, W.C.
Partner: UNT Libraries Government Documents Department

Improvement of tubulars used for fracturing in hot dry rock wells

Description: Completion of hot dry rock wells as it is currently envisioned, requires that hydraulic fracturing be used to develop a heat extraction reservoir and to provide low impedance flow paths between the designated water injection and production wells. Recent fracturing operations at measured depths from 11,400 ft to 15,300 ft at the Fenton Hill Hot Dry Rock Geothermal Test Site have resulted in numerous failures of tubulars caused by the high fracturing pressures, corrosive environment and large treatment volumes at high flow rates. Two new fracturing strings were designed and purchased. Physical and chemical properties exceeding API specifications were demanded and supplied by the manufacturers. These tubulars have performed to design specifications.
Date: April 1, 1984
Creator: Nicholson, R.W.; Dreesen, D.S. & Turner, W.C.
Partner: UNT Libraries Government Documents Department

A comparative study of RF and induction linac approaches to phase rotation of a muon bunch in the production region of a {mu}{sup +}- {mu}{sup {minus}} collider

Description: RF and induction linac approaches to phase rotation of the muon bunch have been studied. Shorter accelerator length, lower power consumption and shorter bunch length favor the RF linac approach. An important outstanding research issue is the operation of RF cavities within 2 - 3 meters of the production target and the accompanying very high radiation background.
Date: October 1996
Creator: Turner, W. C. & Kirk, H. G.
Partner: UNT Libraries Government Documents Department

Control of longitudinal collective behavior in the Muon Collider rings

Description: The longitudinal bunch collective effects in a Muon Collider ring are theoretically examined. The situation involves an intense bunch, a short bunch, a small momentum compaction, a rather large impedance compared with the stability threshold criterion, and luminosity life time limited by muon decay to a thousand turns. Qualitative descriptions of stability are given and a scaling law for the instability threshold is derived. Numerical simulation results for the impedance-related instabilities are given for two cases of current interest - a 250 GeV x 250 GeV demonstration machine and a 2 TeV x 2 TeV high energy machine. The results of these simulations are in good agreement with the predictions of the scaling law and show that the longitudinal collective effects are controllable with a proper choice of parameters (viz. rf voltage, rf frequency, linear and non-linear longitudinal chromaticity).
Date: May 1, 1997
Creator: Cheng, Wen-Hao; Sessler, A.M. & Turner, W.C.
Partner: UNT Libraries Government Documents Department

Studies of the beam-beam interaction for the LHC

Description: The authors have used the beam-beam simulation code CBI to study the beam-beam interaction for the LHC. We find that for nominal LHC parameters, and assuming only one bunch per beam, there are no collective (coherent) beam-beam instabilities. We have investigated the effect of sweeping one of the beams around the other (a procedure that could be used as a diagnostic for head-on beam-beam collisions). We find that this does not cause any problems at the nominal current, though at higher currents there can be beam blow-up and collective beam motion. consequence of quadrupole collective effects.
Date: March 1, 1999
Creator: Krishnagopal, S.; Furman, M.A. & Turner, W.C.
Partner: UNT Libraries Government Documents Department

Synchrotron radiation and beam tube vacuum in a Very Large Hadron Collider, Stage 1 and Stage 2 VLHC

Description: Synchrotron radiation induced photodesorption in particle accelerators may lead to pressure rise and to beam-gas scattering losses, finally affecting the beam lifetime [1]. We discuss the beam tube vacuum in the low field Stage 1 and Stage 2 Very Large Hadron Collider VLHC. Since VLHC Stage 1 has a room temperature beam tube, a non-evaporable getter (NEG St101 strip) pumping system located inside a pumping antechamber, supplemented by lumped ion pumps for pumping methane is considered. In Stage 2, the {approx}100 K beam screen, or liner, illuminated by the synchrotron radiation, is inserted into the magnet cold bore. Cryo-pumping is provided by the cold bore kept at 4.2 K, through slots covering the beam screen surface. Possible beam conditioning scenarios are presented for reaching design intensity, both for Stage 1 and 2. The most important results are summarized in this paper.
Date: June 30, 2001
Creator: Pivi, M.; Turner, W.C.; Bauer, P. & Limon, P.
Partner: UNT Libraries Government Documents Department

Absorbers for the high luminosity insertions of the LHC

Description: At design luminosity and inelastic cross section {sigma}{sub pp} = 80mb there are 8 {times} 10{sup 8} inelastic collisions per second at the high luminosity interaction points IP1 and IP5 of the LHC. These interactions give rise to {approximately} 0.9 kW of power in collision products leaving an IP in each direction. The inelastic collision power carried off by neutrals, mostly neutrons and photons, in each direction and intercepted by neutral absorbers (TAN) has been estimated with the MARS13 code to be 210W. Similarly the collision power escaping the beam tube and incident on the front face of the inner triplet quadrupole absorber (TAS) has been estimated to be {approximately} 270W, mostly carried by charged pions and photons. Special purpose absorbers must intercept this power to prevent quenching the inner triplet quadrupoles (Q1 to Q3) and the twin aperture magnets outside the second beam separation dipole D2. Because of the high incident flux of collision products near zero degrees the absorbers are natural places to consider for the location of radiation hard gas ionization detectors which could be used for: (1) measurement of luminosity, (2) measurement of the beam transverse dimensions at the IP and (3) feedback control of the colliding beam centers at the IP`s to maximize luminosity. The following sections describe: (1) the conceptual design of the absorbers, (2) the radiation deposition and activation calculations and (3) the possibilities for instrumentation.
Date: June 1, 1998
Creator: Turner, W.C.; Hoyer, E.H. & Mokhov, N.V.
Partner: UNT Libraries Government Documents Department

Beam tube vacuum in a Very Large Hadron Collider; Stage 1 VLHC

Description: Synchrotron radiation induced photodesorption in particle accelerators may lead to pressure rise and to beam-gas scattering losses, finally affecting the beam lifetime. We discuss the beam tube vacuum in the low field Stage 1 Very Large Hadron Collider VLHC. Since VLHC Stage 1 has a room temperature beam tube, a non-evaporable getter (NEG St101 strip) pumping system located inside a pumping antechamber, supplemented by lumped ion pumps for pumping methane is considered. A possible beam conditioning scenario is presented for reaching design intensity. The most important results are summarized in this paper. More detailed reports of the calculations will be presented at the PAC2001 Conference, Chicago, IL to be held in June 2001, and at the Snowmass Conference, CO, to be held on July 2001.
Date: April 20, 2001
Creator: Pivi, M. & Turner, W.C.
Partner: UNT Libraries Government Documents Department

Multi-channel neutral analyzer-system

Description: Design and calibration of a 15 channel multi-channel analyzer for analysis of energetic neutral particles escaping a hot plasma are discussed. Features of the analyzer include a frequency response from DC to 50 kHz, spatial resolution, mass resolution, and data acquisition and processing for 15 points on the energy distribution that are simultaneously recorded. Another feature of the system is the ability to radially scan the plasma. An rf ion source is used to provide ions and neutrals used for calibration of a reference single channel analyzer. This analyzer is, in turn, used to calibrate the multi-channel analyzer over the energy range 500 eV to 40 keV. A brief description of the data processing system is included. (RME)
Date: September 14, 1977
Creator: Nexsen, Jr., W. E.; Turner, W. C. & Cummins, W. F.
Partner: UNT Libraries Government Documents Department

Computational compact torus experiment

Description: We describe a typical 2D magnetohydrodynamic (MHD) calculation of rundown of plasma in a coaxial, magnetized gun and injection of the plasma and reconnection of the embedded magnetic fields to form a compact toroidal plasma.
Date: December 24, 1980
Creator: Eddleman, J.L.; McNamara, B.; Nash, J.K.; Shearer, J.W. & Turner, W.C.
Partner: UNT Libraries Government Documents Department