Chandra Pillai

Ac, La, and Ce radioimpurities in 225Ac produced in 40–200 MeV proton irradiations of thorium

Abstract Accelerator production of 225Ac addresses the global supply deficiency currently inhibiting clinical trials from establishing 225Acs therapeutic utility, provided that the accelerator product is of sufficient radionuclidic purity for patient use. Two proton activation experiments utilizing the stacked foil technique between 40 and 200 MeV were employed to study the likely co-formation of radionuclides expected to be especially challenging to separate from 225Ac. Foils were assayed by nondestructive γ-spectroscopy and by α-spectroscopy of chemically processed target material. Nuclear formation cross sections for the radionuclides 226Ac and 227Ac as well as lower lanthanide radioisotopes 139Ce, 141Ce, 143Ce, and 140La whose elemental ionic radii closely match that of actinium were measured and are reported. The predictions of the latest MCNP6 event generators are compared with measured data, as they permit estimation of the formation rates of other radionuclides whose decay emissions are not clearly discerned in the complex spectra collected from 232Th(p,x) fission product mixtures.

Cross sections from proton irradiation of thorium at 800 MeV

Nuclear formation cross sections are reported for 65 nuclides produced from 800-MeV proton irradiation of thorium foils. These data are useful as benchmarks for computational predictions in the ongoing process of theoretical code development and also to the design of spallation-based radioisotope production currently being considered for multiple radiotherapeutic pharmaceutical agents. Measured data are compared with the predictions of three MCNP6 event generators and used to evaluate the potential for 800-MeV productions of radioisotopes of interest for medical radiotherapy. In only a few instances code predictions are discrepant from measured values by more than a factor of two, demonstrating satisfactory predictive power across a large mass range. Similarly, agreement between measurements presented here and those previously reported is good, lending credibility to predictions of target yields and radioimpurities for high-energy accelerator-produced radionuclides.

High speed EPICS data acquisition and processing on one VME board

A custom VME board is being designed at the Los Alamos Neutron Science Center (LANSCE) for high speed signal acquisition and processing. While it is desirable to design around the EPICS/VME platform, it can be difficult to process high-speed signals with long record lengths. The relatively slow data path between the IOC and the general-purpose computer makes real time computations impossible. Commercial VME processor boards can be used, but the data must still flow over the VME backplane in lieu of other traffic. This custom board is designed to overcome this problem by acquiring and processing the signal in one place, with the processed result presented at the VME interface instead of the raw data. The board consists of multiple front-end signal conditioners/digitizer cards plugged into the foundation 6U VME board with an embedded digital signal processor (DSP). The DSP is programmed in C to process the raw signal any way the user wants before writing results into a VME register map. The present front-end conditioner/digitizer cards are being designed with the LANSCE low momentum detector in mind, but other variations on this card could be developed. The architecture is flexible enough to deploy in many accelerator applications.

A multiwire proportional chamber system for monitoring low momentum beam in accelerators

A diagnostic is being developed at the Los Alamos Neutron Science Center (LANSCE) for the purpose of identifying low momentum beam tails in the linear accelerator. These tails must be eliminated in order to maintain the transverse and longitudinal beam size. Instead of the currently used phosphor camera system, this instrument consists of a multiwire proportional chamber (MWPC) front end coupled to an EPICS compliant VME-based electronics package. Low momentum tails are detected with a resolution of 5 mm in the MWPC at a high dispersion point near a bending magnet. While phosphor is typically not sensitive in the nano amp range, the MWPC is sensitive down to about a pico amp. The electronics package will process the signals from each of the MWPC wires to generate an array of beam currents at each of the lower energies. The electronics will have a wideband analog front end, active antialias filter, and high-speed analog to digital converter for each wire. Data from multiple wires will be processed with an embedded digital signal processor and results placed in a set of VME registers. An EPICS application will assemble the data from these VME registers into a display of beam current vs. beam energy (momentum) in the LANSCE control room. This display will update at least once per second, but will be a representation of the real time signal processing results from the electronics package.

Proposed beam diagnostics instrumentation for the LANSCE refurbishment project

Presently, the Los Alamos National Laboratory is in the process of planning a refurbishment of various subsystems within its Los Alamos Neutron Science Center accelerator facility. A part of this LANSCE facility refurbishment will include some replacement of and improvement to existing older beam-diagnostics instrumentation. While plans are still being discussed, some instrumentation that is under improvement or replacement consideration are beam phase and position measurements within the 805-MHz side-coupled cavity linac, slow wire profile measurements, typically known as wire scanners, and possibly additional installation of fast ionization-chamber loss monitors. This paper will briefly describe the requirements for these beam measurements, what we have done thus far to answer these requirements, and some of the technical issues related to the implementation of the instrumentation.

H + - and H - -beam position and current jitter at LANSCE

During the CY2005 and CY2006 Los Alamos Neutron Science Center (LANSCE) beam runs, beam-development shifts were performed in order to acquire and analyze beam-current and beam-position jitter data for both the LANSCE H+ and H- beams. These data were acquired using three beam-position monitors (BPMs) from the 100-MeV Isotope Production Facility (IPF) beam line and three BPMs from the Switchyard (SY) transport line at the end of the LANSCE 800-MeV linac. The two types of data acquired, intermacropulse and intramacropulse, were analyzed for statistical and frequency characteristics as well as various other correlations including comparing their phase-space characteristics in a coordinate system of transverse angle versus transverse position. This paper will briefly describe the measurements required to acquire these jitter data, the analysis of these data, and some interesting implications to beam operation.

Acquisition and Initial Analysis of H+‐ and H−‐Beam Centroid Jitter at LANSCE

During the 2005 Los Alamos Neutron Science Center (LANSCE) beam runs, beam current and centroid‐jitter data were observed, acquired, analyzed, and documented for both the LANSCE H+ and H− beams. These data were acquired using three beam position monitors (BPMs) from the 100‐MeV Isotope Production Facility (IPF) beam line and three BPMs from the Switchyard transport line at the end of the LANSCE 800‐MeV linac. The two types of data acquired, intermacropulse and intramacropulse, were analyzed for statistical and frequency characteristics as well as various other correlations including comparing their phase‐space like characteristics in a coordinate system of transverse angle versus transverse position. This paper will briefly describe the measurements required to acquire these data, the initial analysis of these jitter data, and some interesting dilemmas these data presented.

Comparison of profile measurements and TRANSPORT beam envelope predictions along the 80-m LANSCE pRad beamline

Here we report a comparison between the simulation of beam phase-space and profile distributions with diagnostic measurements. TRANSPORT, a particle transport code, was used for the prediction of a 800 MeV proton beam envelope from the end of the linac to the proton radiography (pRad) facility (a total length of 80 meters). The beam profile was measured at key positions along the beamline using wire scanners and gated CCD camera systems. These measurements were compared to their respective points along the simulated beamline. The predicted beam envelope and measured data correspond within expected errors.

Space-charge Neutralization of 750-keV H⁻ Beam at LANSCE

The injector part of Los Alamos Neutron Science Center (LANSCE) includes a 750-keV Hbeam transport located upstream of the Drift Tube Linac. Space charge effects play an important role in the beam transport therein [1]. A series of experiments were performed to determine the level of beam space charge neutralization, and time required for neutralization. Measurements performed at different places along the structure indicate significant variation of neutralized space charge beam dynamics along the beamline. Results of measurements were compared with numerical simulations using macroparticle method and envelope equations to determine values of the effective beam current after neutralization, and effective beam emittance, required for beam tuning. 750 KEV LANSCE BEAM TRANSPORT The H beam injector includes a cesiated, multicuspfield, surface –production ion source and two-stage lowenergy beam transport line. In the first stage, extracted beam is accelerated up to 80 keV, and then is transported through a solenoid, electrostatic deflector, a 4.5 bending magnet, and a second solenoid. The 670 kV CockroftWalton column accelerates beam up to an energy of 750 keV. The 750 keV LEBT (see Fig. 1) consists of a quadrupole lattice, 81 and 9 bending magnets, slowwave chopper, RF bunchers, an electrostatic deflector, diagnostics and steering magnets to prepare beam for injection into the Drift Tube Linac (DTL). Slit-collector beam emittance measurements at 750 keV are performed at five locations: 1) TBEM1 (just after the Cockroft Walton column), 2) TBEM2 (downstream of the chopper), 3) TBEM3 (downstream of the 81 bend before RF pre-buncher), 4) TBEM4 (between the first RF (pre)buncher and second (main) buncher), and 5) TDEM1 (before the entrance to the DTL). BEAM EMITTANCE SCANS Ionization of residual gas by transported particles is an important factor of low-energy beam transport. Fig. 2 illustrates a typical spectrum of residual gas in the 750 keV H transport channel obtained from a Residual Gas Analyzer installed in the middle of the channel. Main components are H2 (48%), H2O (38%) and N2 (9%). Fractions of other components are significantly smaller. Typical total pressure measured by ion gauges along the transport channel range from 5 10 Torr to 10 Torr. _______________________ *Work supported by US DOE under contract DE-AC52-06NA25396 batygin@lanl.gov Figure 1: Layout of 750-keV H Low Energy Beam Transport of LANSCE. Figure 2: Residual gas analyzer scan. A series of beam emittance scans along 750 keV H beam transport were performed to determine time and level of space charge neutralization of the beam, value of effective beam current under space–charge neutralization, and the value of effective beam emittance. Measurements were done as pair measurements between each pair of emittance stations TBEM1–TBEM2, TBEM2-TBEM3, TBEM3–TBEM4, TBEM4–TDEM1. Measurements were performed with an ion source pulse length of 825 μs. The emittance was sampled within the last 50 s of the ion source pulse. The beam pulse start time was varied between  = 10 – 575 s before the emittance sampling through delay in the 80 kV electrostatic deflector. Typical value of H beam current at 750 keV was 14 – 17 mA. 10 5th International Particle Accelerator Conference IPAC2014, Dresden, Germany JACoW Publishing ISBN: 978-3-95450-132-8 doi:10.18429/JACoW-IPAC2014-THPRO097

Existing muon beams at LAMPF

The Stopped Muon Channel (SMC) at LAMPF is heavily used for a variety of muon experiments: (1) Muon Catalyzed Fusion (μCF), Muon Spin Rotation (μSR), and Muonic X-rays using decay muon beams; (2) Muon Level-Crossing Resonance (μLCR), Rare Decays, and Muonium Hyperfine Structure & Muon Magnetic Moment using surface muon beams; (3) Laser Polarized Muonic Atoms using cloud beams.