Physical Review Special Topics-accelerators and Beams, 2006
In a first beam dynamics validation experiment for a new Pulse Line Ion Acceleration (PLIA) conce... more In a first beam dynamics validation experiment for a new Pulse Line Ion Acceleration (PLIA) concept, the predicted energy amplification and beam bunching were experimentally observed. Beam energy modulation of -80 to +150keV was measured using a PLIA input voltage waveform of -21 to +12kV. Ion pulses accelerated by 150 keV, and bunching by a factor of 4 were simultaneously
Near-term High Energy Density Physics (HEDP) experiments prefer low mass ion sources and high cur... more Near-term High Energy Density Physics (HEDP) experiments prefer low mass ion sources and high current density. Thermionic emission from solid materials, such as, large diameter (2-10 cm) K^+ alumino-silicate surface ionization emitters have proven to be very reliable, long-...
Near-term High Energy Density Physics (HEDP) experiments prefer low mass ion sources and high cur... more Near-term High Energy Density Physics (HEDP) experiments prefer low mass ion sources and high current density. Thermionic emission from solid materials, such as, large diameter (2-10 cm) K^+ alumino-silicate surface ionization emitters have proven to be very reliable, long-lived, and supply current densities in the range of 2.5-10.0 mA/cm^2 for several experiments including the High Current Experiment (HCX) and Neutralized Drift Compression Experiment (NDCX). Recently, low mass alkali alumino-silicate materials coated onto porous tungsten substrates were fabricated and their space-charge limited ion emission properties were measured at an extraction electric field of 40 kV/cm and pulse duration of 20mus. In our presentation, Li+ and Na+ alumino-silicate ion sources will be compared to the previously characterized K+ and Cs+ alumino-silicate emitters. This data will show that either sodium or lithium ion sources can meet HEPD requirements.
The High Current Experiment (HCX) is exploring heavy-ion beam transport in an alternating gradien... more The High Current Experiment (HCX) is exploring heavy-ion beam transport in an alternating gradient quadrupole focusing channel at a scale representative of the low-energy end of an induction linac driver for fusion energy production. A primary mission of this experiment is to investigate aperture fill factors (F = diameter of maximum beam excursion / aperture diameter) acceptable for the transport of space-charge dominated heavy-ion beams at high space-charge intensity (line-charge density ˜ 0.2 microC/m) over long pulse durations (> 4 microsec). We present the phase space evolution of a K+ ion beam transported (F>0.5) through 4 magnetic quadrupoles. Transverse phase space is measured including particle loss from beam halo. Upstream phase space measurements constrain beam parameters and are used to initialize simulations. The consequences for beam control and fill-factors in longer lattice experiments will be discussed.
Future WDM and HEDP experiments may use solenoids for transverse focusing of low energy, space-ch... more Future WDM and HEDP experiments may use solenoids for transverse focusing of low energy, space-charge dominated ion beams during acceleration. An experiment to transport a 10 μs long, singly charged potassium ion bunch at an ion energy of 0.3 MeV and current of 45 mA through a solenoid lattice (STX) has been commissioned at LBNL. The beam should establish a Brillouin-flow condition, particle rotation at the Larmor frequency, with fields greater than 2T. The principal objectives of the STX are to match and transport the space-charge dominated ion beam and to study mechanisms that would degrade beam quality such as focusing-field aberrations, beam halo, spacing of lattice elements, and electron-cloud and gas effects. A qualitative comparison of experimental and calculated results are presented, which include time resolved transverse phase-space of the beam at different diagnostic planes throughout the focusing lattice, beam current density and beam-induced gas desorption, ionization and electron effects. (This work was supported by the U.S. D.O.E. under DE-AC02-05H11231)
Lawrence Berkeley National Laboratory, Apr 27, 2006
Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the perfor... more Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the performance of storage rings. Earlier measurements of electron energy distribution and flux to the walls provided only a relative electron-cloud density. We have measured electron accumulation using ions expelled by the beam. The ion energy distribution maps the depressed beam potential and gives the dynamic cloud density. Clearing electrode current reveals the static background cloud density, allowing the first absolute measurement of the time-dependent electron-cloud density during the beam pulse.
In developing high current and high brightness beams for HIF, an ion source was constructed aimin... more In developing high current and high brightness beams for HIF, an ion source was constructed aiming at producing > 0.5 A of Ar^+. The chamber is 33 cm in diameter with multicusp permanent magnets to confine plasma. RF power ( ˜11 MHz, > 10 kW) is applied to the source via a 2-turn, 11-cm diameter antenna inside the chamber for producing beam pulses of 20 mus at up to 10 Hz. Ions are extracted from the ion source in an array of beamlets that will be merged into a single beam later. With 5 mA per beamlet, the beamlet current density is ˜ 100 mA/cm^2. Plasma probe data has recorded > 200 mA/cm^2 of ion saturation current near the chamber center with 2 mT of fill pressure. We will present measurements of the extracted current density as a function of RF power and gas pressure, the beam rise time, current density uniformity, energy dispersion (due to charge exchange) and the percentage of high charge state ions in the beam.
The High Current Experiment (HCX) is exploring heavy-ion beam transport in an alternating gradien... more The High Current Experiment (HCX) is exploring heavy-ion beam transport in an alternating gradient quadrupole focusing channel at a scale representative of the low-energy end of an induction linac driver for fusion energy production. A primary mission of this experiment is to investigate aperture fill factors (F = diameter of maximum beam excursion / aperture diameter) acceptable for the transport
... Capacitive coupling • Magnitude ~500 times expelled ion current from beam: • Shield with grid... more ... Capacitive coupling • Magnitude ~500 times expelled ion current from beam: • Shield with grids. Subtract remaining contribution. Signal to noise: • Signals as low as ~1 µA, noise from spark-gaps • Shield, preamps near collectors. B Page 7. ...
The High Current Experiment (HCX) is exploring heavy-ion beam transport in an alternating gradien... more The High Current Experiment (HCX) is exploring heavy-ion beam transport in an alternating gradient quadrupole focusing channel at a scale representative of the low-energy end of an induction linac driver for fusion energy production. A primary mission of this experiment is to investigate aperture fill factors (F = diameter of maximum beam excursion / aperture diameter) acceptable for the transport
Physical Review Special Topics-accelerators and Beams, 2006
In a first beam dynamics validation experiment for a new Pulse Line Ion Acceleration (PLIA) conce... more In a first beam dynamics validation experiment for a new Pulse Line Ion Acceleration (PLIA) concept, the predicted energy amplification and beam bunching were experimentally observed. Beam energy modulation of -80 to +150keV was measured using a PLIA input voltage waveform of -21 to +12kV. Ion pulses accelerated by 150 keV, and bunching by a factor of 4 were simultaneously
Near-term High Energy Density Physics (HEDP) experiments prefer low mass ion sources and high cur... more Near-term High Energy Density Physics (HEDP) experiments prefer low mass ion sources and high current density. Thermionic emission from solid materials, such as, large diameter (2-10 cm) K^+ alumino-silicate surface ionization emitters have proven to be very reliable, long-...
Near-term High Energy Density Physics (HEDP) experiments prefer low mass ion sources and high cur... more Near-term High Energy Density Physics (HEDP) experiments prefer low mass ion sources and high current density. Thermionic emission from solid materials, such as, large diameter (2-10 cm) K^+ alumino-silicate surface ionization emitters have proven to be very reliable, long-lived, and supply current densities in the range of 2.5-10.0 mA/cm^2 for several experiments including the High Current Experiment (HCX) and Neutralized Drift Compression Experiment (NDCX). Recently, low mass alkali alumino-silicate materials coated onto porous tungsten substrates were fabricated and their space-charge limited ion emission properties were measured at an extraction electric field of 40 kV/cm and pulse duration of 20mus. In our presentation, Li+ and Na+ alumino-silicate ion sources will be compared to the previously characterized K+ and Cs+ alumino-silicate emitters. This data will show that either sodium or lithium ion sources can meet HEPD requirements.
The High Current Experiment (HCX) is exploring heavy-ion beam transport in an alternating gradien... more The High Current Experiment (HCX) is exploring heavy-ion beam transport in an alternating gradient quadrupole focusing channel at a scale representative of the low-energy end of an induction linac driver for fusion energy production. A primary mission of this experiment is to investigate aperture fill factors (F = diameter of maximum beam excursion / aperture diameter) acceptable for the transport of space-charge dominated heavy-ion beams at high space-charge intensity (line-charge density ˜ 0.2 microC/m) over long pulse durations (> 4 microsec). We present the phase space evolution of a K+ ion beam transported (F>0.5) through 4 magnetic quadrupoles. Transverse phase space is measured including particle loss from beam halo. Upstream phase space measurements constrain beam parameters and are used to initialize simulations. The consequences for beam control and fill-factors in longer lattice experiments will be discussed.
Future WDM and HEDP experiments may use solenoids for transverse focusing of low energy, space-ch... more Future WDM and HEDP experiments may use solenoids for transverse focusing of low energy, space-charge dominated ion beams during acceleration. An experiment to transport a 10 μs long, singly charged potassium ion bunch at an ion energy of 0.3 MeV and current of 45 mA through a solenoid lattice (STX) has been commissioned at LBNL. The beam should establish a Brillouin-flow condition, particle rotation at the Larmor frequency, with fields greater than 2T. The principal objectives of the STX are to match and transport the space-charge dominated ion beam and to study mechanisms that would degrade beam quality such as focusing-field aberrations, beam halo, spacing of lattice elements, and electron-cloud and gas effects. A qualitative comparison of experimental and calculated results are presented, which include time resolved transverse phase-space of the beam at different diagnostic planes throughout the focusing lattice, beam current density and beam-induced gas desorption, ionization and electron effects. (This work was supported by the U.S. D.O.E. under DE-AC02-05H11231)
Lawrence Berkeley National Laboratory, Apr 27, 2006
Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the perfor... more Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the performance of storage rings. Earlier measurements of electron energy distribution and flux to the walls provided only a relative electron-cloud density. We have measured electron accumulation using ions expelled by the beam. The ion energy distribution maps the depressed beam potential and gives the dynamic cloud density. Clearing electrode current reveals the static background cloud density, allowing the first absolute measurement of the time-dependent electron-cloud density during the beam pulse.
In developing high current and high brightness beams for HIF, an ion source was constructed aimin... more In developing high current and high brightness beams for HIF, an ion source was constructed aiming at producing > 0.5 A of Ar^+. The chamber is 33 cm in diameter with multicusp permanent magnets to confine plasma. RF power ( ˜11 MHz, > 10 kW) is applied to the source via a 2-turn, 11-cm diameter antenna inside the chamber for producing beam pulses of 20 mus at up to 10 Hz. Ions are extracted from the ion source in an array of beamlets that will be merged into a single beam later. With 5 mA per beamlet, the beamlet current density is ˜ 100 mA/cm^2. Plasma probe data has recorded > 200 mA/cm^2 of ion saturation current near the chamber center with 2 mT of fill pressure. We will present measurements of the extracted current density as a function of RF power and gas pressure, the beam rise time, current density uniformity, energy dispersion (due to charge exchange) and the percentage of high charge state ions in the beam.
The High Current Experiment (HCX) is exploring heavy-ion beam transport in an alternating gradien... more The High Current Experiment (HCX) is exploring heavy-ion beam transport in an alternating gradient quadrupole focusing channel at a scale representative of the low-energy end of an induction linac driver for fusion energy production. A primary mission of this experiment is to investigate aperture fill factors (F = diameter of maximum beam excursion / aperture diameter) acceptable for the transport
... Capacitive coupling • Magnitude ~500 times expelled ion current from beam: • Shield with grid... more ... Capacitive coupling • Magnitude ~500 times expelled ion current from beam: • Shield with grids. Subtract remaining contribution. Signal to noise: • Signals as low as ~1 µA, noise from spark-gaps • Shield, preamps near collectors. B Page 7. ...
The High Current Experiment (HCX) is exploring heavy-ion beam transport in an alternating gradien... more The High Current Experiment (HCX) is exploring heavy-ion beam transport in an alternating gradient quadrupole focusing channel at a scale representative of the low-energy end of an induction linac driver for fusion energy production. A primary mission of this experiment is to investigate aperture fill factors (F = diameter of maximum beam excursion / aperture diameter) acceptable for the transport
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