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Development of a RAMI Program for LANSCE upgrade

Description: Improvement of beam availability is a prime objective of the present LANSCE (Los Alamos Neutron Scattering Center) Upgrade. A RAMI (reliability, availability, maintainability, and inspectability) program is being developed to identify the most cost-effective improvements to achieve the availability goal. The beam-delivery system is divided into subsystems appropriate for the modeling of availability. The availability of each subsystem is determined from operation data and assessment of individual component designs. These availability data are incorporated in an availability model to predict the benefit of improvement projects to achieve cost-benefit prioritization. Examination of the data also identifies a comprehensive list of factors affecting availability. A good understanding of these factors using root-cause analysis is essential for availability improvement. This paper describes the RAMI program and the development of the availability model.
Date: May 1, 1995
Creator: Chan, K.C.D.; Hutson, R.L.; Macek, R.J.; Tallerico, P.J. & Wilkinson, C.A.
Partner: UNT Libraries Government Documents Department

Relativistic atomic beam spectroscopy II

Description: We are requesting support for a postdoctoral person to participate in H{sup -} studies at Los Alamos. In addition, we are requesting funding for a state-of-the-art YAG laser system that would allow us to obtain data at three times our present rate with improved beam quality.
Date: December 31, 1991
Partner: UNT Libraries Government Documents Department

Simulation studies of the LAMPF proton linac

Description: The LAMPF accelerator consists of two 0.75-MeV injectors, one for H{sup +} and the other for H{sup {minus}}, a separate low-energy beam transport (LEBT) line for each beam species, a 0.75 to 100-MeV drift-tube linac (DTL) operating at 201.25-MHz, a 100-MeV transition region (TR), and a 100 to 800-MeV side-coupled linac (SCL) operating at 805-MHz. Each LEBT line consists of a series of quadrupoles to transport and transversely match the beam. The LEBT also contains a prebuncher, a main buncher, and an electrostatic deflector. The deflector is used to limit the fraction of a macropulse which is seen by the beam diagnostics throughout the linac. The DTL consists of four rf tanks and uses singlet FODO transverse focusing. The focusing period is doubled in the last two tanks by placing a quadrupole only in every other drift-tube. Doublet FDO transverse focusing is used in the SCL. The TR consists of separate transport lines for the H{sup +} and H{sup {minus}} beams. The pathlengths for the two beams differ, by introducing bends, so as to delay arrival of one beam relative to the other and thereby produce the desired macropulse time structure. Peak beam currents typically range from 12 to 18-mA for varying macropulse lengths which give an average beam current of 1-mA. The number of particles per bunch is of the order 10{sup 8}. The work presented here is an extension of previous work. The authors have attempted to do a more complete simulation by including modeling of the LEBT. No measurements of the longitudinal structure of the beam, except phase-scans, are performed at LAMPF. The authors show that, based on simulation results, the primary causes of beam spill are inefficient longitudinal capture and the lack of longitudinal matching. Measurements to support these claims are not presently made at LAMPF. ...
Date: May 1, 1995
Creator: Garnett, R.W.; Gray, E.R.; Rybarcyk, L.J. & Wangler, T.P.
Partner: UNT Libraries Government Documents Department

Linac-driven spallation-neutron source

Description: Strong interest has arisen in accelerator-driven spallation-neutron sources that surpass existing facilities (such as ISIS at Rutherford or LANSCE at Los Alamos) by more than an order of magnitude in beam power delivered to the spallation target. The approach chosen by Los Alamos (as well as the European Spallation Source) provides the full beam energy by acceleration in a linac as opposed to primary acceleration in a synchrotron or other circular device. Two modes of neutron production are visualized for the source. A short-pulse mode produces 1 MW of beam power (at 60 pps) in pulses, of length less than 1 ms, by compression of the linac macropulse through multi-turn injection in an accumulator ring. A long-pulse mode produces a similar beam power with 1-ms-long pulses directly applied to a target. This latter mode rivals the performance of existing reactor facilities to very low neutron energies. Combination with the short-pulse mode addresses virtually all applications.
Date: May 1, 1995
Creator: Jason, A.J.
Partner: UNT Libraries Government Documents Department

A theoretical study of the electron-proton instability in a long proton pulse

Description: The electron-proton instability of a long, intense, and partially neutralized proton bunch is studied by numerically solving the equations of motion for the line centroid of the proton beam and the line centroid of the trapped electrons. The formalism takes into account the effects of variable line densities and alternating-gradient focusing. Good qualitative agreement between the computational results and experimental observations was obtained when applying the theory to the Los Alamos Proton Storage Ring (PSR). Both the case of a clean extraction gap and the case with a few percent of protons in the extraction gap were studied. It is found that with only a few percent neutralization, the PSR beam can become unstable in both cases. The same equations and method were used to study the stability of the proton beam in the accumulator ring of the proposed LANSCE II spallation-neutron source. The results indicate that the e-p instability can also occur in the LANSCE II accumulator ring for only a few percent neutralization.
Date: May 1, 1995
Creator: Wang, Tai-Sen F.
Partner: UNT Libraries Government Documents Department

Electron clearing in the Los Alamos Proton Storage Ring

Description: The instability observed in the Los Alamos Proton Storage Ring (PSR) has been tentatively identified as an electron-proton instability. A source of electrons must exist for this instability to occur. The PSR injection section contains the stripper foil, and therefore provides several strong sources of electrons. An electron clearing system was installed in the injection section to clear out these electrons. The system comprised: (1) a foil biasing system to clear the SEM and thermionic electrons, (2) a pair of low-field bending magnets with a Faraday cup to clear the convoy electrons, and (3) two pairs of clearing electrodes, one upstream and one downstream of the stripper foil, to clear the remaining electrons. This paper discusses the design and performance of the Electron Clearing System, and its effect on the instability. Also presented are some results from other charge-collection experiments that suggest there is also substantial electron production in parts of the ring other than the injection section.
Date: May 1, 1995
Creator: Plum, M.A.; Allen, J.; Borden, M.J.; Fitzgerald, D.H.; Macek, R.J. & Wang, T.S.
Partner: UNT Libraries Government Documents Department

Recent progress on beam stability study in the PSR

Description: A fast transverse instability has been observed in the Los Alamos Proton Storage Ring (PSR) when the injected beam intensity reaches more than 2 {times} 10{sup 13} protons per pulse. Understanding the cause and control of this instability has taken on new importance as the neutron-scattering community considers the next generation of accelerator-driven spallation-neutron sources, which call for peak-proton intensities of 10{sup 14} per pulse or higher. Previous observations and theoretical studies indicate that the instability in the PSR is most likely driven by electrons trapped within the proton beam. Recent studies using an experimental electron-clearing system and voltage-biased pinger-electrodes for electron clearing and collection support this hypothesis. Experiments have also been performed to study the instability threshold when varying the electron production rate. Theoretical studies include a computer simulation of a simplified model for the e -- p instability and the investigation of possible electron confinement in the ring-element magnetic fields. This paper reports some recent results from these studies.
Date: May 1, 1995
Creator: Wang, T.; Channell, P. & Cooper, R.
Partner: UNT Libraries Government Documents Department

Ion-chamber-based loss monitor system for the Los Alamos Meson Physics Facility

Description: A new loss monitor system has been designed and installed at the Los Alamos Meson Physics Facility (LAMPF). The detectors are ion chambers filled with N{sub 2} gas. The electronics modules have a threshold range of 1:100, and they can resolve changes in beam loss of about 2% of the threshold settings. They can generate a trip signal in 2 {mu}s if the beam loss is large enough; if the response time of the Fast Protect System is included the beam will be shut off in about 37 {mu}s.
Date: May 1, 1995
Creator: Plum, M.A.; Brown, D.; Browman, A. & Macek, R.J.
Partner: UNT Libraries Government Documents Department

Electric fields, electron production, and electron motion at the stripper foil in the Los Alamos Proton Storage Ring

Description: The beam instability at the Los Alamos Proton Storage Ring (PSR) most likely involves coupled oscillations between electrons and protons. For this instability to occur, there must be a strong source of electrons. Investigation of the various sources of electrons in the PSR had begun. Copious electron production is expected in the injection section because this section contains the stripper foil. This foil is mounted near the center of the beam pipe, and both circulating and injected protons pass through it, thus allowing ample opportunity for electron production. This paper discusses various mechanisms for electron production, beam-induced electric fields, and electron motion in the vicinity of the foil.
Date: May 1, 1995
Creator: Plum, M.
Partner: UNT Libraries Government Documents Department

Design and performance of the LAMPF 1-1/4 MW klystron modulator

Description: From 11th modulator symposium; New York, New York, USA (18 Sep 1973). A design for a very reliable single-triode modulator for a 11/4 MW modulating-anode klystron is presented. The operating voltage is 86 kV and the variable pulse length ranges from 200 4mmsec to 1.2 msec. The basic modulator circuit, which uses a novel Zener diode bias circuit, and several of the individual components are described in detail. Over 140,000 high-voltage hours have been accumulated on these modulators. The principal failure mechanism is grid emission from the triode. These failures can be anticipated and repaired during a normal maintenance period. The triode is then reprocessed and reused. Tube life data and a summary of the failures modes are presented. (auth)
Date: April 30, 1974
Creator: Tallerico, P.J.; Cady, R.L. & Doss, J.D.
Partner: UNT Libraries Government Documents Department

Report on Los Alamos Pion Facility (LAMPF)

Description: The status of LAMPF is reviewed, and the experimental areas are briefly discussed. The experimental areas include the Energetic Pion Channel and Spectrometer (EPICS), Low- Energy Pion Channel (LEP), Stopped Muon Channel, Pion and Particle Physics Channel (P/sup 3/), Nucleon Physics Laboratory (NPL), High- Resolution Proton Spectrometer (HRS), Nuclear Chemistry, and the Neutrino Facility. (WHK)
Date: September 1, 1973
Creator: Crowe, K.M.
Partner: UNT Libraries Government Documents Department

LAMPF reliability history and program

Description: Many years of service of the 800-MeV LAMPF H{sup +}/H{sup {minus}} linac offers the opportunity to evaluate the long-term reliability characteristics of a high-power machine, which with up to 800-kW beam power available is as close to an ADTT machine as exists in the world today. Records from the last 15 years of operation were analyzed for trends and areas of deteriorating reliability or disproportionate downtime and used to support engineering judgment on facility refurbishment to regain beam availability. This round of analysis has helped define a further level of detail and automation to be implemented in availability recording. Interesting features which emerge from the history include a clear measurement of the lower availability in the first operating cycle following extended maintenance periods, and a consistent picture of the highest availability to be expected in extended operating periods with the facility as used and maintained. The results provide a starting point for informed discussion of reliability goals.
Date: September 1, 1994
Creator: van Dyck, O.
Partner: UNT Libraries Government Documents Department

Calibration of the LAMPF E-960 polarized target

Description: This note is mainly about the offline corrections for the target polarization measurements of E-960. For the sake of minimizing the number of separate documents, I have also included my recent thoughts about the target constant, in Sec. 6. The E-960 data-taking was done in two separate runs. With respect to having an operative NMR system, the runs dated from 27-AUG-87 to 10-DEC-87 and from 14-AUG-88 to 6-OCT-88.These runs will be referred to as the ``1987`` and ``1988`` runs, respectively. Because of the press of intervening projects, I have been unable until now to give my attention to the 1988 run of E-960. The information developed below in Secs. 3--5 is the result of my (belated) attempt to do so. A draft memo dated January 4, 1988 was previously distributed, which concerned the polarization correction factors for the 1987 run. I have reproduced the material from that memo in Sec. 2, for the sake of completeness. Also, since the analysis of the 1988 run has raised some questions about the appropriateness of the older analysis, I have augmented the material from that memo with some of the background observations and calculations that underlay its conclusions, to facilitate a comparison of the two runs. In Sec. 4 I have made a final synthesis of the observations made during the two runs, and it is there that one wig find my best estimate of the offline polarization corrections for both runs.
Date: December 23, 1992
Creator: Hill, D. A.
Partner: UNT Libraries Government Documents Department