Angular dose variations from 4- to 6-MV rod-pinch diode experiments on the asterix pulsed-power generator

Swanekamp, S.B.; Allen, R.J.; Commisso, R.J.; Cooperstein, G.; Mosher, D.; Young, F.C.; Vermare, C.; Delvaux, J.; Horde, Y.; Merle, E.; Nicolas, R.; Nore, D.; Pierret, O.; Rosol, Y.R.; Tailleur, Y.; Верон, Лаурент; Bayol, F.; Garrigues, A.; Delbos, C.; Nicot, G.; Oliver, B.V.; Rose, D. V.; Maenchen, J.

doi:10.1109/ppc.2003.1277756

Cited by 8 publications

(5 citation statements)

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“…For the ASTERIX experiments, [19]- [21] tungsten or gold anode rods of 1.0-, 1.6-, 2.0-, and 3.0-mm diameter are used with ranging from 11 to 16. The anode rod extends 16 mm beyond the 3-mm-thick cathode annulus and, for most shots, is tapered to a point over the last 10 mm.…”

Section: Analysis Of Asterix Angular Dose-rate Measurementsmentioning

confidence: 99%

“…The ASTERIX results and related numerical simulations indicate that the angular dose distribution from a RPD is peaked in the backward direction and most of the radiation in positive polarity is headed toward the generator along the length of the rod [21]. This suggests that high-voltage RPD experiments should be performed in negative polarity to maximize the extracted dose [22].…”

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confidence: 99%

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Evaluation of Self-Magnetically Pinched Diodes up to 10 MV as High-Resolution Flash X-Ray Sources

Swanekamp

Cooperstein

Schumer

et al. 2004

IEEE Trans. Plasma Sci.

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The merits of several high-resolution, pulsed-powerdriven, flash X-ray sources are examined with numerical simulation for voltages up to 10 MV. The charged particle dynamics in these self-magnetically pinched diodes (SMPDs), as well as electron scattering and energy loss in the high-atomic-number target, are treated with the partic by coupling the output from LSP with the two-dimensional component of the integrated tiger series of Monte Carlo electron/photon transport codes, CYLTRAN. The LSP/CYLTRAN model agrees well with angular dose-rate measurements from positive-polarity rod-pinch-diode experiments, where peak voltages ranged from 5.2-6.3 MV. This analysis indicates that, in this voltage range, the dose increases with angle and is a maximum in the direction headed back into the generator. This suggests that high-voltage rod-pinch experiments should be performed in negative polarity to maximize the extracted dose. The benchmarked LSP/CYLTRAN model is then used to examine three attractive negative-polarity diode geometry concepts as possible high-resolution radiography sources for voltages up to 10 MV. For a 2-mm-diameter reentrant rod-pinch diode (RPD), a forward-directed dose of 740 rad(LiF) at 1 m in a 50-ns full-width at half-maximum radiation pulse is predicted. For a 2-mm-diameter nonreentrant RPD, a forward-directed dose of 1270 rad(LiF) is predicted. For both RPDs, the on-axis X-ray spot size is comparable to the rod diameter. A self-similar hydrodynamic model for rod expansion indicates that spot-size growth from hydrodynamic effects should be minimal. For the planar SMPD, a forward-directed dose of 1370 rad(LiF) and a similar X-ray spot size are predicted. These results show that the nonreentrant RPD and the planar SMPD are very attractive candidates for negative-polarity high-resolution X-ray sources for voltages of up to 10 MV.Index Terms-Bremsstrahlung, coupled electron-photon transport, electron beams, flash X-radiography, high-power diodes, ion beams, Monte Carlo, particle-in-cell.

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Section: Analysis Of Asterix Angular Dose-rate Measurementsmentioning

confidence: 99%

mentioning

confidence: 99%

Evaluation of Self-Magnetically Pinched Diodes up to 10 MV as High-Resolution Flash X-Ray Sources

Swanekamp

Cooperstein

Schumer

et al. 2004

IEEE Trans. Plasma Sci.

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“…For comparison, the proton current fraction from a reentrant RP diode at 10 MV is estimated to be 45%. [4] Therefore, the electron current on the high-Z target increases significantly for the negative polarity geometries and could increase the dose by about 40%. Heating the anode prior to the shot could further increase the electron current by eliminating the source of the low-Z ions.…”

Section: Resultsmentioning

confidence: 99%

“…The recent experiments on Asterix at 4 -6 MV [3] and related numerical simulations [4] suggest that 1.4 -2 times more radiation is produced in the backwards direction because most of the electrons approach the tapered anode at angles close to 180". At higher voltages, the asymmetry in electron angles-of-incidence is more strongly coupled to the radiation distribution, thus the desire for higher x-ray yield in the forward direction will require more difficult negative polarity geometries for voltages above 4 MV.…”

Section: Introductionmentioning

confidence: 98%

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Considerations of rod-pinch diode operation in negative polarity for radiography

Cooperstein

Swanekamp

Schumer

et al.

Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference (IEEE Cat. No.03CH37472)

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A bstr-actNegative polarity diode geometries are investigated from 2 -10 M V with 2D PIC simulations for application to radiography. Rod-pinch (RP) diodes with nonreentrant blunt tip anodes (anode does not pass through a cathode apemre) are investigated and compared to selfmagnetically-pinched (SMP) diodes with similar geometries. At lower voltages, reentrant RP geometries are needed so that the space-charge-limited (SCL) current will exceed the critical current. Once self-pinchmg is achieved, the electron flow pattems in both types of diodes are similar, but it is speculated that RP diodes will maintain their small spot size for the duration of the pulse. At higher voltage, negative polarity non-reentrant RP designs can take advantage of smaller spot sizes, larger forward-going dose, reduced ion losses, and resistance to gap closure by decoupling the spot from the diode impedance. Reduced ion currents increase the electron current on the high-Z target which could increase the dose by about 40% compared to a positive polarity RP geometry.

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Negative polarity rod pinch diode experiments on the astertx generator

Etchessahar¹,

Rosol²,

Caron³

et al. 2010

2010 Abstracts IEEE International Conference on Plasma Science

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Angular dose variations from 4- to 6-MV rod-pinch diode experiments on the asterix pulsed-power generator

Cited by 8 publications

References 0 publications

Evaluation of Self-Magnetically Pinched Diodes up to 10 MV as High-Resolution Flash X-Ray Sources

Evaluation of Self-Magnetically Pinched Diodes up to 10 MV as High-Resolution Flash X-Ray Sources

Considerations of rod-pinch diode operation in negative polarity for radiography

Negative polarity rod pinch diode experiments on the astertx generator

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