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Steski, D.

Publications and source records attributed to Steski, D..

18 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Novel high-energy ion implantation facility using a 15 MV Tandem Van de Graaff accelerator

The implantation depths required for the development and fabrication of future generations of silicon carbide (SiC) semiconductor devices require ion energies that are well above the capabilities of most conventional ion implanters. To generate implantation profiles that extend from more than 10 μm to the surface of the wafer, a wide range of energy ions (kV to 10 s of MeV) is required. We developed a novel multi-energy implantation system that satisfies these requirements using heavy ion beams from one of the Brookhaven National Laboratory’s two 15 MV Tandem Van de Graaff accelerators. This system is described, including the dosimetry approach and the available ion species and intensities. Finally, an example of a measured implantation profiles in SiC is shown and compared to simulations.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Calcium and lithium ion production for laser ion source

Calcium and lithium ion beams are required by NASA Space Radiation Laboratory at Brookhaven National Laboratory to simulate the effects of cosmic radiation. To identify the difficulties in providing such highly reactive materials as laser targets, both species were experimentally tested. Plate shaped lithium and calcium targets were fabricated to create ablation plasmas with a 6 ns 1064 nm neodymium-doped yttrium aluminum garnet laser. We found significant oxygen contamination in both the Ca and Li high charge state beams due to the rapid oxidation of the surfaces. A large spot size, low power density laser was used to create low charge state beams without scanning the targets. The low charge state Ca beam did not have any apparent oxygen contamination, showing the potential to clean the target entirely of oxide with a low power beam once in the chamber. The Li target was clearly still oxidizing in the chamber after each low power shot. To measure the rate of oxidation, we shot the low power laser at the target repeatedly at 10 s, 30 s, 60 s, and 120 s interval lengths, showing a linear relation between the interval time and the amount of oxygen in the beam.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Proton beam production by a laser ion source with hydride target

We studied proton beam production from a laser ion source using hydrogen rich target materials. In general, gas based species are not suitable for laser ion sources since formation of a dense laser target is difficult. In order to achieve reliable operation, we tested hydride targets using a sub nanosecond Q-switched Nd-YAG laser, which may help suppress target material consumption. We detected enough yields of protons from a titanium hydride target without degradation of beam current during the experiment. The combination of a sub nanosecond laser and compressed hydride target may provide stable proton beam.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

RHIC operation with asymmetric collisions in 2015

To study low-x shadowing/saturation physics as well as other nuclear effects [1], [2], proton-gold (p-Au, for 5 weeks) and proton-Aluminum (p-Al, for 2 weeks) collisions were provided for experiments in 2015 at the Relativistic Heavy Ion Collider (RHIC), with polarized proton beam in the Blue ring and Au/Al beam in the Yellow ring. The special features of the asymmetric run in 2015 will be introduced. The operation experience will be reviewed as well in the report.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Operation experience of p-Carbon polarimeter in RHIC

The spin physics program in Relativistic Heavy Ion Collider (RHIC) requires fast polarimeter to monitor the polarization evolution on the ramp and during stores. Over past decade, the polarimeter has evolved greatly to improve its performance. These include dual chamber design, monitoring camera, Si detector selection (and orientation), target quality control, and target frame modification. The preamp boards have been modified to deal with the high rate problem, too. The ultra thin carbon target lifetime is a concern. Simulations have been carried out on the target interaction with beam. Modification has also been done on the frame design. Extra caution has been put on RF shielding to deal with the pickup noises from the nearby stochastic cooling kickers. This paper summarizes the recent operation performance of this delicate device.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

RHIC polarized proton-proton operation at 100 GeV in Run 15

The first part of RHIC Run 15 consisted of ten weeks of polarized proton on proton collisions at a beam energy of 100 GeV at two interaction points. In this paper we discuss several of the upgrades to the collider complex that allowed for improved performance. The largest effort consisted in commissioning of the electron lenses, one in each ring, which are designed to compensate one of the two beam-beam interactions experienced by the proton bunches. The e-lenses raise the per bunch intensity at which luminosity becomes beam-beam limited. A new lattice was designed to create the phase advances necessary for a beam-beam compensation with the e-lens, which also has an improved off-momentum dynamic aperture relative to previous runs. In order to take advantage of the new, higher intensity limit without suffering intensity driven emittance deterioration, other features were commissioned including a continuous transverse bunch-by-bunch damper in RHIC and a double harmonic RF cature scheme in the Booster. Other high intensity protections include improvements to the abort system and the installation of masks to intercept beam lost due to abort kicker pre-fires.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

The RHIC polarized source upgrade

The RHIC polarized H{sup −} ion source is being upgraded to higher intensity and polarization for use in the RHIC polarization physics program at enhanced luminosity RHIC operation. The higher beam intensity will allow reduction of the longitudinal transverse beam emittance at injection to AGS to reduce polarization losses in AGS. There is also a planned RHIC luminosity upgrade by using the electron beam lens to compensate the beam-beam interaction at collision points. This upgrade is also essential for future BNL plans for a high-luminosity electron-proton (ion) Collider eRHIC. The basic limitations on the high-intensity H{sup −} ion beam production in charge-exchange collisions of the neutral atomic hydrogen beam in the Na-vapor jet ionizer cell were experimentally studied.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

The RHIC Polarized Source Upgrade

The basic limitations on the high-intensity H - ion beam production were experimentally studied in charge-exchange collisions of the neutral atomic hydrogen beam in the Na- vapor jet ionizer cell. These studies are the part of the polarized source upgrade (to 10 mA peak current and 85% polarization) project for RHIC. In the source the atomic hydrogen beam of a 5-10 keV energy and total (equivalent) current up to 5 A is produced by neutralization of proton beam in pulsed hydrogen gas target. Formation of the proton beam (from the surface of the plasma emitter with a low transverse ion temperature ~0.2 eV) is produced by four-electrode spherical multi-aperture ion-optical system with geometrical focusing. The hydrogen atomic beam intensity up t o 1.0 A /cm 2 (equivalent) was obtained in the Na-jet ionizer aperture of a 2.0 cm diameter. At the first stage of the experiment H- beam with 36 mA current, 5 keV energy and ~1.0 cm·mrad normalized emittance was obtained using the flat grids and magnetic focusing. The experimental results of the high-intensity neutral hydrogen beam generation and studies of the charge-exchange polarization processes of this intense beam will be presented.

43 PARTICLE ACCELERATORS↗