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DOE OSTI2023

LANSCE CCL Performance Limits

This report summarizes the performance limits of the LANSCE Coupled-Cavity Linac (CCL). These results are captured or summarized directly from the references cited. This report was written in support of the LANSCE Modernization Project (LAMP). Many factors contribute to the performance limits of the CCL accelerator system. One performance limit is set by the CCL mechanical structure and available cooling. Heating of the structure is ultimately linked to the operating RF duty factor of the CCL. Another performance limit is set by the maximum RF and beam duty factors that can be supported by the 805-MHz klystrons and associated HVDC power supplies. The RF and HVDC systems also set limits for the maximum peak beam current that can be accelerated in the CCL. And finally, a maximum beam current limit is set by the beam dynamics determined by the details of the CCL physics design (number of cells per CCL tank, accelerating gradients, magnetic focusing lattice, beam losses, etc.). This limit can be informed by both simulation results and beam measurement data, if available. A detailed explanation of each performance limit is given in the sections below. The results are summarized in the table below. In all cases, it is assumed that the CCL and the RF system are operating in their nominal beam production configuration – nominal magnet set points and nominal cavity fields, unless otherwise specified.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Preliminary Design of a LAMP DTL (Update)

Present report is a continuation of the previously published report LA-UR-23-26600 from 19-Jun-2023 and incorporates the mentioned report as its part. All the additional information is contained in the part III of this report, the DTL Transverse Focusing Scheme. A preliminary Drift Tube Linac (DTL) layout was designed to create an algorithm for developing the conceptual design of the proposed LANSCE Accelerator Modernization Project (LAMP) final section: the proton linear accelerator from 3 MeV to 100 MeV. Preceding reports describe the proposed layouts of the LEBT, the RFQ, and the MEBT subsections of the linac. Initial estimates of the needed RF power for the DTL are also presented in the report. Present report describes the initial layout of the DTL and the first longitudinal beam dynamics (BD) results of the simulations in simplified models. The part III of this report includes the transverse focusing scheme and transverse BD in details.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

LAMP-PSR Scoping Studies Report

This report summarizes work performed from July – September 2023, performing an initial evaluation for the LANSCE Proton Storage Ring upgrade option “B.” The studies identified potential pathsforward, performing initial beam dynamics studies, and surveying various technology options different aspects of the upgrade. Taken together, the studies provide an “early look” at the feasibility, challenges and alternative methods for pursuing Option “B,” and give guidance towards more detailed design concept development needed as work progresses. Generally speaking, no major obstacles were identified in pursuing the Option “B” PSR upgrade path in terms of the machine physics or overall system architecture. Several areas of concern have been identified; we note that these primarily center on technology choice and must be addressed regardless of the upgrade path selected, and none of the concerns are considered insurmountable.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

MEBT Bunchers: System Design Document (SDD)

The LAMP Medium Energy Beam Transport (MEBT) transfers bunched beam at the energy 3 MeV from RFQ to the Drift-Tube Linac (DTL) entrance. The beam particles (protons or H- ) in the LAMP MEBT have velocity β = v/c = 0.08, where v is the beam velocity, c is the speed of light. The MEBT bunchers keep beam bunches from spreading longitudinally as they propagate through the MEBT, where some unwanted bunches are removed by a chopper to create a required beam pattern. The MEBT bunchers are RF cavities operating at the frequency 201.25 MHz; possible design options were considered in.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

NorthStar Helium Cooling System. Final Report on LANL Contribution

From the beginning of NNSA support to the NorthStar development of a production facility for the medical isotope Molybdenum-99 (Mo99), LANL has been responsible for the design and testing of a target and its cooling. The target is comprised of a stack of Mo100 disks separated by coolant flow gaps between the disks and between the first disk and a housing window, which separates the target and its coolant from the vacuum of the beam line. The target, and therefore its cooling requirements, evolved steadily over the years of system development

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2023

Initial Conditioning of the Rod-style RFQ

The RFQ test stand will allow new sources to be tested and will provide information on the performance of our RFQ designs. The RFQ must sustain the high peak power that will be necessary for bunching and accelerating beam, and that peak power must be sustained at a duty factor that is higher than other facilities that use similar rod-style RFQs. The conditioning of the RFQ allows both requirements to be tested, and in addition the intricacies of its operation are discovered and can be corrected for future work. In addition, the conditioning procedure was able to be done concurrently with the source development.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Derivative-free optimization of a rapid-cycling synchrotron

Here, we develop and solve a constrained optimization model to identify an integrable optics rapid-cycling synchrotron lattice design that performs well in several capacities. Our model encodes the design criteria into 78 linear and nonlinear constraints, as well as a single nonsmooth objective, where the objective and some constraints are defined from the output of Synergia, an accelerator simulator. We detail the difficulties of the 23-dimensional simulation-constrained decision space and establish that the space is nonempty. We use a derivative-free manifold sampling algorithm to account for structured nondifferentiability in the objective function. Our numerical results quantify the dependence of solutions on constraint parameters and the effect of the form of objective function.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

High-gradient performance of a prototype accelerator cavity for a 3 GeV proton radiography booster

This paper reports the design, fabrication, and results of the high-gradient conditioning and testing for a two-cell, π -mode, standing wave normal-conducting prototype booster cavity for the proposed 3 GeV proton linac upgrade at Los Alamos Neutron Science Center. Increasing the energy of proton beam from the existing 800 MeV to 3 GeV will improve resolution of the proton radiography by up to 10 times. The proposed energy boost can be achieved with a compact normal-conducting high-gradient radio-frequency (rf) linac section. The C-band section of the booster linac was designed with optimized-shaped copper accelerator cavities with distributed rf coupling. A short two-cell test prototype structure was designed for the frequency of 5.712 GHz, fabricated, and tested at the C-band Engineering Research Test Facility in New Mexico (CERF-NM) at Los Alamos National Laboratory. The maximum klystron power coupled into the test structure was 8.3 MW with 1 μ s pulse length and 100 Hz repetition rate. The breakdown probabilities were recorded as functions of the accelerating gradient and peak surface fields. Operation of the test cavity at accelerating gradients of up to 100 MV / m was demonstrated. Published by the American Physical Society 2024

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Preliminary Design of a LAMP DTL

A preliminary Drift Tube Linac (DTL) layout was designed to create an algorithm for developing the conceptual design of the proposed LANSCE Accelerator Modernization Project (LAMP) final section: the proton linear accelerator from 3 MeV to 100 MeV. Preceding reports describe the proposed layouts of the LEBT, the RFQ, and the MEBT subsections of the linac. Initial estimates of the needed RF power for the DTL are also presented in the report. Present report describes the initial layout of the DTL and the first longitudinal beam dynamics results of the simulations n simplified models. The follow-up reports will include the transverse focusing scheme and beam dynamics in details. Present report in the last section will only describe the planned focusing scheme, based on the existing LANCE DTL.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Niowave Power Converter Modeling and Testing

Niowave has designed, built and is now using in-beam a low power (up to 10 kW) lead bismuth eutectic (LBE) converter. In this concept, an electron beam is passed through a falling layer of LBE, converting the electron to neutrons which then pass into a vessel which is functionally a subcritical reactor configuration. A detailed report has been written by Niowave, entitled “LBE Neutron Converter Manual.” The LANL contribution has been modeling, followed by a flow visualization model made in quartz. The LANL contribution is reported herein.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Target Optimization Study: Tolerance Sensitivity

A Work Package was initiated to investigate the potential for target optimization. The current design is made up of 82 disks 0.5 mm thick spaced 0.25 mm apart for helium coolant flow. This disk thickness and gap width are a result of continual increases is beam power and hence volumetric heating rate. Thickening the disks would mean higher disk temperatures, but this would be weighed against the prospect of fewer, thicker disks and wider coolant gap spaces, and the relaxed tolerances that would result. Fabrication of the target holder would be easier and less expensive, and target assembly would also be easier.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Charge per Micro-Pulse Calculation for Ideal Lujan and WNR beams

A complete redesign of the LANSCE front-end is currently under development for the Los Alamos Modernization Project (LAMP). This includes the replacement of the traditional Cockroft-Walton injection system to the newer radiofrequency quadrupole (RFQ) standard. LANSCE accelerates both H- and H+ beams and therefore requires an unconventional application for RFQ systems. A new facility could consider using an independent RFQ for each beam species. However, with the tight space of the LANSCE injector facility, it would prove difficult to instrument. Our initial studies have shown that a single RFQ could be used. The negatively- and positively-charged direct current (DC) beams are shaped, bunched, and accelerated out of phase to each other, with very little interaction. This would work for all possible H+ beam gates and most H- Beam gates. However, a challenge arises with the Weapons Neutron Research (WNR) beam structure that requires the acceleration of bunched beams at higher charge density per pulse. The Long Bunch Enable Gate (LBEG) used for the Lujan center is the best example of a standard injector beam gate. The beam gate, or Macro-Pulse (MP), is 625-us long, separated by at least 8.3 ms. A chopper is used to dice the MP into 1750 mini-Pulses (mP), which are 290-ns wide. After chopping, the MP contains 100,000 micro-Pulses (uP), which are generated by the linac acceleration structure modulated at 201.25 MHz; that is, the micro-Pulses are separated 5 ns apart from each other. The H+ beam structure will be very similar once a chopper is added to its transport. However, the Multi-Pulse Enable Gate (MPEG) used for WNR is significantly different in structure. In this case, the mP is chopped to be only 35-ns wide. This width is then rotated into a single 201.25 MHz RF bucket using the Low Frequency Buncher (LFB). This is proving difficult for the RFQ design in the LAMP upgrade. We began investigating the amount of current sent to WNR for two reasons. Firstly, we wanted to find a solution to avoid using the Low Frequency Buncher to simplify the LAMP RFQ design. It is simple to inject and accelerate a 35 mA DC beam in the LAMP RFQ (this is done in numerous accelerator facilities). However, injecting a short bunch with a larger current (once compressed to 5 ns to meet the RFQ frequency) may be difficult. Second, we have a technique called PSR2WNR in which we do not employ the Low Frequency Buncher, but rather accumulate 5 LBEG uP (5 ns) in the PSR and deliver the accumulated beam to WNR every 1.8 us. As a result, we could provide to WNR with five accumulated LBEG uPs every shot. The goal here is to create a rapid kicker with a frequency response of 555 kHz. DARHT-II and other accelerator facilities have constructed kickers of this type for other uses, and our engineers consider this technology as feasible.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Niowave Design and Analysis of a 200 kW Converter

LANL is providing support to Niowave Inc. on the design and analysis of a 200 kW converter. The current design of the 200 kW (40 MeV, 5 mA electron beam) converter consists of LBE flowing from the top to the bottom. When compared to the Mk.5 20 kW converter, which flowed LBE from the bottom, flowing over a divider plate to create a waterfall, the 200 kW converter eliminates the divider plate, which would otherwise have melted with the higher beam power. Because the LBE flows from the top to the bottom, alternate methods to the divider plate need to be utilized to ensure a stable flow that minimizes splashing at the bottom of the LBE waterfall, while maintaining a uniform LBE thickness at the beam, and steady LBE flow at the desired flow rate.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

LEBT Buncher / Feed Forward / Frequency Generation: System Design Document (SDD)

The LAMP Low Energy Beam Transport (LEBT) transfers a continuous beam at 100 keV from the ion source to RFQ in LEBT. A LEBT buncher imposes an energy tilt to initiate velocy bunching in the chopped beam pulse about 25 ns long to form a short MPEG bunch. One possible option for the LEBT buncher based on a two-gap LC-circuit driven structure was considered, which is similar to the existing LANSCE low-frequncy buncher (LFB). Another possible option is a non-resonant element driven by a pulse-forming-network that provides a single pulse at the repetition frequency of MPEG beam, with a period of 1.8 µs. The LEBT operation is synchronized with the accelerator timing system.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

LAMP DTL Scoping Studies (Technical Report)

The present studies are based on the preliminary design efforts, and on the Scoping Studies of the “Strawman” design of LAMP front-end upgrade, referred in the text below to as “Feb.2024 Iteration”, presented in. The main accomplishment of present studies was substantial increase of the fidelity of the beam dynamics simulations in the proposed drift tube linac (DTL). The main accent was on development of the methodology for calculation of the longitudinal (synchrotron) and transverse (betatron) oscillations frequencies (phase advance per focusing period) values and providing the accelerating structure focusing lattice that has safe parameters of such oscillations to avoid unwanted emittance growth and possible beam halo formation. The resulting values of the oscillations phase advances are presented in Table 1, and in Figure 5 in the main body of the report. Special efforts were made to achieve the RF power consumption within limits of the existing RF power system and make sure that DTL fits in the existing tunnel. The LAMP scope does not suggest any additional building and/or tunnel construction. Table 1 summarizes some of these results, as well as Table 3 in the main body of the report.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

LAMP Technical Readiness Evaluation Report (Rev. 1)

An internal preliminary evaluation of Critical Technology Elements (CTEs) for the LANSCE Modernization Project (LAMP) was completed. Corresponding Technical Readiness Levels (TRLs) were also determined for all subsystems using the criteria of DOE G 413.3-4A, Technical Readiness Assessment Guide. The scope of the evaluation was limited to the project Work Breakdown Structure (WBS) elements as defined for the RFQ Injector and Drift Tube Linac (DTL) systems only. Integration of Instrumentation and Controls (I&C) and Safety Systems was not considered, although specific technologies as related to the RFQ and DTL systems were included. Other elements of the project such as Shielding, System Design, Technical Management, and additional facility integration needed to enable off-line testing and pre-installation commissioning were also not evaluated. Each technical subsystem element was evaluated for technical readiness, however, not all were found to meet the criteria for a CTE. Only two subsystem elements were determined to meet the CTE criteria. Their associated TRLs are summarized in the table below. These subsystem elements of the project have the lowest technical readiness due to either being new, novel or modified, requiring additional R&D before being capable of meeting the project Key Performance Parameters (KPPs) and subsystem requirements, or present technology exists but has not yet been demonstrated in a relevant environment. All other subsystems were determined to have a TRL of 8, indicating that actual operating systems exist having similar performance requirements as needed for LAMP. Details of the technical readiness evaluation for each subsystem is given in the following sections of this report.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

LAMP Technical Readiness Evaluation Report

An internal preliminary evaluation of Critical Technology Elements (CTEs) for the LANSCE Modernization Project (LAMP) was completed in 2023. This included determining corresponding Technical Readiness Levels (TRLs) for all subsystems using the criteria of DOE G 413.3-4A, Technical Readiness Assessment Guide. This revised report includes a summary of the recent design modifications required to meet the project Key Performance Requirements (KPPs), some of which may reduce technical risk to the project. These recent design modifications include: • Further optimization of the low-energy and medium-energy beam transport regions (LEBT and MEBT, respectively), including relocation of various functional elements (ie choppers, kickers, and bunchers). • An additional H - ion source to separate ion-source function based on beam delivery requirements. • A high-repetition-rate pulsed kicker magnet to select/merge the two H ion beams into a common low-energy beam transport. • Modification and further optimization to a more conventional RFQ design. Performance of the RFQ has been optimized to deliver the required three types of beams while meeting the project KPPs. • The addition of a second chopper in the medium-energy beam transport (MEBT) line to reduce the required pulser voltages. The scope of the evaluation was limited to the project Work Breakdown Structure (WBS) elements as defined for the RFQ Injector and Drift Tube Linac (DTL) systems only. Integration of Instrumentation and Controls (I&C) and Safety Systems was not considered, although specific technologies as related to the RFQ and DTL systems were included. Other elements of the project such as Shielding, System Design, Technical Management, and additional facility integration needed to enable off-line testing and pre-installation commissioning were also not evaluated. Each technical subsystem element was evaluated for technical readiness, however, not all were found to meet the criteria for a CTE. Three subsystem elements were determined to meet the CTE criteria. Their associated TRLs are summarized in the table below. These subsystem elements of the project have the lowest technical readiness due to either being new, novel or modified, requiring additional R&D before being capable of meeting the project Key Performance Parameters (KPPs) and subsystem requirements, or present technology exists but has not yet been demonstrated in a relevant environment. All other subsystems were determined to have a TRL of 8, indicating that actual operating systems exist having similar performance requirements as needed for LAMP. Details of the technical readiness evaluation for each subsystem is given in the following sections of this report.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

MEBT Chopper System: System Design Document (SDD)

The Medium Energy Beam Transport (MEBT) chopper removes unwanted beam bunches by deflecting them to a target from a bunched beam transported through the MEBT from RFQ to the Drift-Tube Linac (DTL) entrance. The unchopped bunches propagate through the MEBT to DTL, while the deflected bunches are deposited on a target downstream of chopper. The chopper system consists of a deflecting structure, where the beam-deflecting fields are created, and a pulse generator (pulser) that feeds this structure with voltage pulses having the required time pattern. Ideally, the system should turn deflection on and off in the time interval between the bunches to prevent partially chopped / deflected bunches. This usually requires traveling slow-wave chopper structures where the field propagates with the same velocity as the beam, as illustrated in Fig. 1.

43 PARTICLE ACCELERATORS↗