Strong self-focusing of a 7.2 MeV electron beam striking an aluminized mylar target

Vermare, C.; Labrouche, J.; Gabory, P. Le Taillandier de; Villate, D.; Donohue, J.T.

doi:10.1109/27.808927

Cited by 9 publications

(8 citation statements)

References 5 publications

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“…The surface contaminants serve as a source for protons which are commonly found in experiments involving intense electron beam impact [21][22][23]. Simulations modeling a hydrogen anode plasma as described above show depletion of the plasma density as protons are drawn into bipolar flow, and plasma expansion does not occur.…”

Section: Model Parameters For the Smp Diodementioning

confidence: 99%

Anode plasma dynamics in the self-magnetic-pinch diode

Bruner

Welch

Hahn

et al. 2011

Phys. Rev. ST Accel. Beams

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The self-magnetic-pinch diode is being developed as an intense electron beam source for pulsed-powerdriven x-ray radiography. In high-power operation, the beam electrons desorb contaminants from the anode surface from which positive ions are drawn to the cathode. The counterstreaming electrons and ions establish an equilibrium current. It has long been recognized, however, that expanding electrode plasmas can disrupt this equilibrium and cause rapid reduction of the diode impedance and the radiation pulse. Recently developed numerical techniques, which enable simultaneous modeling of particle currents with 10 13 cm À3 densities to plasmas of near solid density, are applied to a model of the self-magnetic-pinch diode which includes the formation and evolution of anode surface plasmas. Two mechanisms are shown to cause rapid impedance loss, anode plasma expansion into the anode-cathode (A-K) gap, and increased ion space-charge near the cathode surface. The former mechanism dominates for shorter A-K gaps, while the latter dominates for longer gaps. Model results qualitatively reproduce the time-dependent impedances measured for this diode.

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Section: Model Parameters For the Smp Diodementioning

confidence: 99%

Anode plasma dynamics in the self-magnetic-pinch diode

Bruner

Welch

Hahn

et al. 2011

Phys. Rev. ST Accel. Beams

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“…Heavy Ta+ ions probably exist, but are not observed, because they are expected to reach the foil #2 after the end of the beam pulse. These results confirm the ionic emission hypothesis [1][2][3][4].…”

Section: Resultssupporting

confidence: 81%

“…It was assigned to the emission of both heavy ions issued from the target material [1], [2] and light ions H+ issued from hydrogen atoms contaminating the target [3], [4]. They are produced by the vaporization of the target.…”

Section: Introductionmentioning

confidence: 99%

A new diagnostic for the measurement of the ionic emission generated by an electron-photon conversion target

Fontaine

Godefroy²,

Guilhem³

et al.

PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268)

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A beam diagnostic made of a double sheet sensor is designed to the search of ions, emitted by an electronphoton conversion target under the impact of an intense relativistic electron beam. This device is tested on the PIVAIR prototype accelerator. Signals attributed to ions emitted from the target are observed for different target elements : Ta, C, Ti, Au and light species are identified by their time of flight. The mean velocities of C+ and H+ ions are found to be respectively equal to 1.2 108 cm/s and 5 108 cm/s for C and Ta targets. The ionic appearance and rise time signals are closed to the expected values. Besides, the current signals are characterized by a plateau to which level corresponds to the Child-Langmuir current (25 A for H+ ions). Furthermore, the fall-off of this signal is found to be in synchronism with the electron beam one. This behaviour represents the deconfinement of the ion beam under the effect of its own space charge. These experimental results confirm the preliminary calculations obtained with the M2V Maxwell-Vlasov PIC code which has been coupled with a ionic emission model.

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“…Different methods were particularly studied to reduce the ion effect: self-biased target [11][12][13][14][15][16][17], barrier foil [6,7,18], target surface laser cleaning [6], time varying final focusing solenoidal lens and beam energy variation [19]. Various analytical models or numerical simulations using particle-incell (PIC) codes were carried out, with various ion species emitted with a space charge limited current (in the Child-Langmuir regime) [12][13][14][17][18][19][20][21][22][23][24][25]. Thus, the ion effect was attributed to the species giving the best agreement with the spot size measurement [11][12][13][14][20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Ion emission at the target of the radiographic devices PIVAIR and AIRIX

Fontaine¹

2007

J. Phys. D: Appl. Phys.

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On an AIRIX facility, a high-intensity electron beam is used to generate an x-ray pulse for radiographic purposes. The measured electron beam spot size is found to be much larger than its computed value. It is shown that this discrepancy is removed considering ion emission at the target, under electron beam interaction. A model has been developed to simulate the plasma produced during the interaction of the electron beam with the target. The predictions have been compared with ion identification results developed on the PIVAIR prototype accelerator as well as with the x-ray spot size and dose measurements obtained on AIRIX. The simulations show that the ion effect can be reduced by placing a thin foil (100 µm thickness) at an appropriate distance from the target to catch the ions emitted and to stabilize the electron beam spot size. The X-spot size is then reduced, as found experimentally on AIRIX. Moreover, for a smaller thickness barrier foil (5 µm), the ion effect can even be suppressed, producing an X-spot size close to that obtained without ion emission.

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Strong self-focusing of a 7.2 MeV electron beam striking an aluminized mylar target

Cited by 9 publications

References 5 publications

Anode plasma dynamics in the self-magnetic-pinch diode

Anode plasma dynamics in the self-magnetic-pinch diode

A new diagnostic for the measurement of the ionic emission generated by an electron-photon conversion target

Ion emission at the target of the radiographic devices PIVAIR and AIRIX

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