The Tokamak as a Neutron Source

Hendel, H. W.; Jassby, D.L.

doi:10.13182/nse90-a27465

Cited by 5 publications

(7 citation statements)

References 63 publications

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“…_:o.02 r_.s,+o.o4 i;.o.32+o.o4=_SEMP2,(2) where Ps is the applied beam power in MW, and rE is the energy confinement time in sec. This formulation is similar to the representation [7,17] where neutron emission has been plotted as a function of beam power (Fig. 4), and the best TFTR results occurred with S_ o¢ p]_s.…”

Section: Empirical Scaling Of Neutron Emissionmentioning

confidence: 74%

“…Since supershot confinement time is independent of beam power [16], the neutron emission at maximum rE is proportional to P_is. In previous publications [17], it was recognized that there was an improvement in neutron emission at low plasma current which we now call out explicitly in Eq. 2.…”

Section: Empirical Scaling Of Neutron Emissionmentioning

confidence: 94%

“…Contribution to the electron density from beam ions, thermal deuterium, and carbon impurities as deduced by Eqs (8),(15),(16),. and(17). (A) is the actual density and (B)is the fractional density.…”

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confidence: 99%

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Neutron emission from TFTR supershots

et al. 1993

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Empirical scaling relations are deduced describing the neutron emission from TFTR supershots using a database that includes all of the supershot plasmas (525) from the 1990 campaign. A physics based scaling for the neutron emission is derived from the dependence of the central plasma parameters on the machine settings and the energy confinement time. This scaling has been used to project the fusion rate for equivalent DT plasmas in TFTR, and to explore the machine operation space that optimizes the fusion rate. Increases in neutron emission are possible by either increasing the toroidal magnetic field or further improving the limiter conditioning

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Section: Empirical Scaling Of Neutron Emissionmentioning

confidence: 74%

Section: Empirical Scaling Of Neutron Emissionmentioning

confidence: 94%

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Neutron emission from TFTR supershots

et al. 1993

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“…This formulation is similar to the representation [7,17] where neutron emission has been plotted as a function of beam power (Fig. 4), and the best TFTR results occurred with S_ o¢ p]_s.…”

Section: Empirical Scaling Of Neutron Emissionmentioning

confidence: 74%

Neutron emission from TFTR supershots

Strachan¹,

Bell²,

Bitter³

et al. 1992

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Empirical scaling relations are deduced describing the neutron emission from TFTR• supershots using a data base that includes all of the supershot plasmas (525) from the 1990 campaign. A physics-based scaling for the neutron emission is derived from the dependence of the central plasma parameters on machine settings and the energy confinement time. Thi:.scaling has been used to project the fusion rate for equivalent DT plasmas in TFTR, aad to explore machine operation space which optimizes the fusion rate. Increases in neutron emission are possible by either increasing the toroidal magnetic field or further improving the limiter conditioning.. 1MIT Plasma Fusion Center, Cambridge, MA 02139 I. INTRODUCTION '4,One goal of the TFTR experimental research program is to achieve scientific breakeven wherein the fusion power produced equals the power required to heat the plasma. Presently, the highest performance TFTR deuterium plasmas are the supershot plasmas [1] which have produced equivalent QDT values _ 1/3 [2] (where "equivalent" is a projection that is defined in Sec. 8). Clearly, there is a need to operate the supershot plasma in a manner that will further optimize its fusion performance.This paper evaluates the statistical dependence of the d(d,n)ZHe fusion neutron emission from TFTR deuterium supershots upon the TFTR machine settings (e.g., plasma current, toroidal magnetic field, neutral beam power, etc.). Empirical and physics-based scaling relations are derived and compared to the neutron emission as well as to that predicted by Q one-dimensional transport codes. The supershot neutron emission is described in terms of a zero-dimensional model which identifies the variables related to the underlying physics of the fusion reactions. This model was used to evaluate equivalent fusion rates for DT plasmas and to suggest machine conditions for optimal performance.The analysis indicates that the primary limitation of the TFTR supershots is the apparent f3-1imit of the supershots when the plasma energy content is about 0.S of the Troyon value [3].Above this limit, TFTR supershots experience some disruptions. Even sporadic disruptions make experiments in the supershot regime difficult due to the sensitivity of supershots to the wall conditions. Another conclusion from the statistical analysis is that the deuterium neutron emission was independent of the neutral beam voltage (from 85 kV to 105 kV).However, considerable improyement was achieved by conditioning the walls with lithium pellet injection. A further improvement is projected by increasing the toroidal magnetic 2 field.The organization of this paper is first to describe the database. Scaling relations are then derived for the neutron emission based upon entirely empirical regression analysis.The measured neutron rates are then compared with those predicted by one-dimensional transport calculations.A zero-dimensional model for the neutron emission is then derived.TFTR supershot scaling for the relevant plasma parameters that describe the classical physics o...

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“…The sensitivity of BF, and ,He counters is such that they can record typically one event for every lo6 neutrons emitted. At TFTR (Hendel and Jassby 1990), sT-60U vishitani et a1 1992) and JET (Jarvis et al 1985), ?35U counters containing about 1 g of fissile material offer a sensitivity of about 1 event per 10' neutrons; these counters are entirely adequate for machines operating with deuterium fuel. However, it is noteworthy that at TFTR one counter loaded with about 18 g of 235U is available for very low yield plasmas and to provide higher efficiency for in-vessel calibration work (see below).…”

Section: 5 And/or 14 Mev Neutronsmentioning

confidence: 99%

Neutron measurement techniques for tokamak plasmas

Jarvis

1994

Plasma Phys. Control. Fusion

138

139

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The present article reviews the neutron measurement techniques that are currently being applied to the study of tokamak plasmas. The range of neutron energies of primary interest is limited to narrow bands around 2.5 and 14MeV, and the variety of measurements that can be made for plasma diagnostic purposes is also restricted. To characterize the plasma as a neutron source, it is necessary only to measure the total neutron emission, the relative neutron emissivity as a function of position throughout the plasma, and the energy spectra of the emitted neutrons. In principle, such measurements might be expected to be relatively easy. That this is not the case is, in part. attributable to practical problems of accessibility to a harsh environment but is mostly a consequence of the time-scale on which the measurements have to be made and of the wide range of neutron emission intensities that have to be-covered; for tokamak studies, the time-scale is of the order of 1 to lOOms and the neutron intensity ranges from 1 0 ' ' to 1oiPs-!.. .

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The Tokamak as a Neutron Source

Cited by 5 publications

References 63 publications

Neutron emission from TFTR supershots

Neutron emission from TFTR supershots

Neutron emission from TFTR supershots

Neutron measurement techniques for tokamak plasmas

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