H. E. Wegner

Single-Event Upset (SEU) Model Verification and Threshold Determination Using Heavy Ions in a Bipolar Static RAM

Single-Event Upset (SEU) response of a bipolar low-power Schottky-diode-clamped TTL static RAM has been observed using Br ions in the 100-240 MeV energy range and 0 ions in the 20-100 MeV range. These data complete the experimental verification of circuit-simulation SEU modeling for this device. The threshold for onset of SEU has been observed by the variation of energy, ion species and angle of incidence. The results obtained from the computer circuit-simulation modeling and experimental model verification demonstrate a viable methodology for modeling SEU in bipolar integrated circuits.

Fully Stripped Heavy Ion Yield vs Energy for Xe and au Ions

The Bevalac is now capable of accelerating U-238 ions to approximately 1 GeV/amu and measurements have shown that fully stripped U-238 ions are produced with good yield at these energies. However, knowing the stripping yields at different energies for U-238 does not allow an accurate prediction for other, lower Z projectiles. Consequently, extensive stripping yield measurements were made for Au-197 and Xe-139 ions. In addition to the stripping measurements from the direct Bevalac beam, pickup measurements were also made with specially prepared bare, one electron, and two electron ions. Since many research groups are considering heavy ion storage rings and/or synchrotrons, the pickup cross section for bare ions is important to estimate beam lifetime in terms of the average machine vacuum. Since the Mylar target provides a pickup probability similar to air, a preliminary analysis of the Xe/sup 54 +/ and U/sup 92 +/ data are presented along with predictions for other ions ranging down to Fe/sup 26 +/. 11 refs., 3 figs., 1 tab.

Tests for Pulsed High Current Heavy Ion Synchrotron Injection with an MP-Tandem Van de Graaff

The new MARK VII high current negative heavy ion source designed by R. Middleton was operated in a pulsed mode to provide 100-200 ¿a negative ion currents in 230 ¿sec square pulses, 10/sec. These pulses, 50-100 times more intense than normal DC beams, were then accelerated by the MP7 Tandem Van de Graaff accelerator while operating at 14 MV. After charge state analysis, the emittance of the pulsed beam was also measured. The very stable accelerator behavior indicated that even higher currents are possible. Values for 16O are: 115 ¿a 16O. injected, 100 MeV 16O6+, 260 ¿a (43.3 p¿a) 1.8 mm.mr and for 32s are: 170 ¿a 32S- injected, 140 MeV 32S9+, 240 ¿a (26.7 p¿a) 0.51 mm.mr. The high intensity and low emittance of these ion beams make them ideal for injection into a synchrotron like the AGS 30 GeV proton accelerator at BNL.

Terminal Ion Source System for the Brookhaven Three-Stage Tandem Facility

A negative ion source has been installed and operated reliably in the high-voltage terminal of the injector accelerator at the Brookhaven Three-stage MP Tandem Van de Graaff Facility. Negative ions extracted directly from an off-axis-type duoplasmatron are focused, mass analyzed, and pre-accelerated to match the beam optics of the acceleration tubes. The ions are then deflected through 90° onto the acceleration axis using an improved electrostatic mirror and steered for optimum beam transmission. Other design features include multiple control rods, TV telemetry, surge-protected power supplies, terminal vacuum pumping, closed-loop liquid cooling and high-speed insulating-gas transfer which permits quick access to the terminal. Beams in excess of 30 ?A, 1H- and 5 ?A, 16O- have been accelerated by the injector to over 9 MeV. Less intense beams have been further accelerated through all three stages to provide 30 MeV, 1H+ and 100 MeV, 16O8+ for experimental use.

The Energy Loss by Charged Particles in Silicon as a Function of Track Orientation

It is important to know the orientation of the crystal axis of silicon semiconductor detectors when they are used for the detection of energetic charged particles in stacked arrays and the particles are expected to traverse all of the detectors. It has been observed that particles that pass through the crystal along the directions of crystal planes or axes lose less energy than those in other directions. This anomalous energy loss spoils the response characteristics of the detector. Various experiments have demonstrated that the penetrating particles tend to move along crystal planes or axes by a process of correlated multiple-coulomb scattering. The experimental evidence for these anomalous characteristics will be reviewed and the degrading effects on the discrimination ability of mass-discrimination detector-systems will be shown. Mass distribution curves were taken for protons, deuterons, tritons, as well as He3 and alpha particles in the 20 to 40 MeV region with a thin silicon?E detector oriented with the (111), (110) and other axis parallel to the penetrating particle direction. The mass separation is appreciably improved when the crystal is oriented so that the direction of the penetrating particles is well away from any of the major crystal planes or axes.

High current beam scanner

It has been shown that a commerciallyavailable scanner can be modified by the addition of an axial marker generator and water-cooled tubes in place of wires so that it can routinely scan high-current accelerator beams up to beam power densities of at least 35 kW/cm2. The versatility of the scanner has been demonstrated by its use with several different accelerators. In all cases, the installation of the scanner involved only simple adaptation to an existing beam pipe and the device was usually in place and functioning properly in less than an hours time.

Improved Four-Stage Accel-Decel Production of Low Energy Highly Stripped Heavy Ions

The two model MP Tandem Van de Graaff accelerators at Brookhaven have been used in a four-stage acceldecel configuration to produce highly stripped low energy heavy ions. The performance in this mode of operation has now been substantially improved by modifications of the second accelerator. The inclined field acceleration tube electrodes at the exit of this accelerator were replaced by straight electrodes, the vacuum was improved and the maximum negative terminal potential was increased. Higher intensity beams of heavier highly stripped ions can now be produced at lower energies than before.

The Three-Stage MP Accelerator Upgrade Program at Brookhaven National Laboratory

The three-stage tandem accelerator facility at Brookhaven National Laboratory (BNL) consists of two model MP tandem Van de Graaff accelerators arranged in line so that MP-6 can inject negative ions up to 10 MeV energy into MP-7 providing a three stage mode of operation. The injector accelerator, MP-6, may also be used as a standard two-stage accelerator having been equipped with an external ion source and target room facility. A description is given of recent improvements and current operating status and performance. Improvements in operation have now provided record electrostatic accelerator heavy ion energies for the research program of 125 MeV /sup 16/O/sup 8 +/ 200 MeV /sup 32/S16/sup +/ and 255 MeV /sup 63/Cu/sup 19 +/

Performance Characteristics of the 30 MeV Three-Stage Tandem Facility at BNL

The 30 MeV 3-stage Van de Graaff facility at Brookhaven National Laboratory achieved the desired operating specifications on July 28, 1970 and has been in operation on various research programs since. The facility consists of two MP Tandem Van de Graaff accelerators arranged in line with a negative ion source installed in the terminal of the first accelerator. The two accelerators can either be used as separate Tandem accelerators or together in a 3-stage configuration. Proton energies as high as 30.5 MeV with currents as high as 4 microamperes have been obtained.

High Current Target for Positive Ion Accelerators

Target development work has led to a design which has been tested with beam power densities near 10 kW/cm2. Use of this design with hydrogen isotopes for targets provides stable, long-lived neutron sources.