N. Simos

Target studies with BNL E951 at the AGS

We report initial results of exposing low-Z solid and high-Z liquid targets to 150-ns, 4/spl times/10/sup 12/ proton pulses with spot sizes on the order of 1 to 2 mm. The energy deposition density approached 100 J/g. Diagnostics included fiberoptic strain sensors on the solid target and high-speed photography of the liquid targets. This work is part of the R&D program of the Neutrino Factory and Muon Collider Collaboration.

A High-Power Target Experiment

We describe an experiment designed as a proof-of-principle test for a target system capable of converting a 4-MW proton beam into a high-intensity muon beam suitable for incorporation into either a neutrino factory complex or a muon collider. The target system is based on exposing a free mercury jet to an intense proton beam in the presence of a high-strength solenoidal magnetic field.

An R&D program for targetry and capture at a neutrino factory and muon collider source

The need for intense muon beams for muon colliders and for neutrino factories based on muon storage rings leads to a concept of 1-4 MW proton beams incident on a moving target that is inside a 20-T solenoid magnet, with a mercury jet as a preferred example. Novel technical issues for such a system include disruption of the mercury jet by the proton beam and distortion of the jet on entering the solenoid, as well as more conventional issues of materials lifetime and handling of activated materials in an intense radiation environment. As part of the R&D program of the Neutrino Factory and Muon Collider Collaboration, an R&D eort related to

Super-Invar as a target for a pulsed high-intensity proton beam

We describe measurements performed on samples consisting of the alloy Super-Invar, which is a candidate material for a robust solid target used in conjunction with an intense pulsed proton beam. A low coefficient of thermal expansion is the characteristic property which makes Super-Invar an attractive target candidate. We have irradiated our samples at the Brookhaven Linac Isotope Producer facility. Tests for variations of the thermal expansion coefficient as a function of inflicted radiation damage are described. The high radiation dose is severely detrimental to its low coefficient of thermal expansion.

Thermodynamic interaction of the primary proton beam with a mercury jet target at a neutrino factory source

This paper addresses the thermodynamic interaction of an intense proton beam with the proposed mercury jet target at a neutrino factory or muon collider source, and the consequences of the generated pressure waves on the target integrity. Specifically, a 24 GeV proton beam with approximately 1.6e13 protons per pulse and a pulse length of 2 nanosec will interact with a 1 cm diameter mercury jet within a 20 Tesla magnetic field. In one option, a train of six such proton pulses is to be delivered on target within 2 microsec, in which case the state of the mercury jet following the interaction with each pulse is critical. Using the equation of state for mercury from the SESAME library, in combination with the energy deposition rates calculated the by the hadron interaction code MARS, the induced 3-D pressure field in the target is estimated. The consequent pressure wave propagation and attenuation in the mercury jet is calculated using an ANSYS code transient analysis, and the state of the mercury jet at the time of arrival of the subsequent pulse is assessed. The amplitude of the pressure wave reaching the nozzle that ejects the mercury jet into the magnetic field is estimated and the potential for mechanical damage is addressed.

Thermal shock analysis of windows interacting with energetic, focused beam of the BNL muon target experiment

In this paper, issues associated with the interaction of a proton beam with windows designed for the muon targetry experiment E951 at BNL are explored. Specifically, a 24 GeV proton beam up to 16 TP per pulse and a pulse length of 100 ns is tightly focused (to 0.5 mm rms radius) on an experimental target. The need to maintain an enclosed environment around the target implies the use of beam windows that will survive the passage of the proton beam. The required beam parameters in such a setting will induce very high thermal, quasi-static and shock stresses in the window structure that exceed the strength of most common materials. In this effort, a detailed analysis of the thermal/shock response of beam windows is attempted through a transient thermal and stress wave propagation formulation that incorporates the energy deposition rates calculated the by hadron interaction code MARS. The thermal response of the window structure and the subsequent stress wave generation and propagation are computed using the finite element analysis procedures of the ANSYS code. This analysis attempts to address issues pertaining to an optimal combination of material, window thickness and pulse structure that will allow for a window to safely survive the extreme demands of the experiment.

First beam tests of the muon collider target test beam line at the AGS

In this report we will describe the muon collider target test beam line which operates off one branch of the AGS switchyard. The muon collider target test facility is designed to allow a prototype muon collider target system to be developed and studied. The beam requirements for the facility are ambitious but feasible. The system is designed to accept bunched beams of intensities up to 1.6/spl times/10/sup 13/ 24 GeV protons in a single bunch. The target specifications require beam spot sizes on the order of 1 mm, 1 sigma rms at the maximum intensity. We will describe the optics design, the instrumentation, and the shielding design. Results from the commissioning of the beam line will be shown.

Integration of the beam scraper and primary collimator in the SNS ring

The collimation system in the SNS ring includes a two-stage collimator consisting of a halo scraper and an appropriate fixed aperture collimator. This unit is placed between the first quadru-pole and the first doublet in the collimation straight section of the ring. The scraper is situated at the exact mid-point between these two magnets, and the fixed aperture collimator fills the space between the scraper and the doublet magnet. The scraper and collimator are surrounded by an outer shield structure. The downstream dose to the doublet and the attached corrector magnet will be estimated for normal operating conditions. In addition, the cooling water activation will be estimated. Finally, the dose at the flange locations will be estimated following machine shutdown.

SNS Collimating System Design — Performance and Integration

The collimating system in the accumulator ring and transfer lines of the Spallation Neutron Source (SNS) project is responsible for stopping 0.1% of the 2 MW beam of 1.0 GeV protons that are in the beam halo. The collimating structures are a combination of movable beam scrapers and stationary absorbers. Specifically, pairs of charge‐exchange foils or scrapers moving in‐and‐out of the beam in the vertical and horizontal directions help guide the halo protons into respective absorbers which consist of an intricate design of a double wall beam tube, a water‐cooled particle bed and radial shielding. Off‐momentum protons, with the help of respective charge exchange foils and a dipole magnet, are directed to a momentum dump consisting of a cooled particle bed downstream of a double‐walled window separating it from the vacuum space. Addressed in this paper is the thermo‐mechanical response and survivability of key components of the collimating system (such as the collimating beam tube in the absorbers, the beam windows and the primary element of the bean scraper structure) in the event of intercept of the full beam under accident conditions. While the potential for the full beam to be intercepted by these components is remote, still special attention will be paid in assessing the amount of full beam (or number of pulses) they can tolerate.The collimating system in the accumulator ring and transfer lines of the Spallation Neutron Source (SNS) project is responsible for stopping 0.1% of the 2 MW beam of 1.0 GeV protons that are in the beam halo. The collimating structures are a combination of movable beam scrapers and stationary absorbers. Specifically, pairs of charge‐exchange foils or scrapers moving in‐and‐out of the beam in the vertical and horizontal directions help guide the halo protons into respective absorbers which consist of an intricate design of a double wall beam tube, a water‐cooled particle bed and radial shielding. Off‐momentum protons, with the help of respective charge exchange foils and a dipole magnet, are directed to a momentum dump consisting of a cooled particle bed downstream of a double‐walled window separating it from the vacuum space. Addressed in this paper is the thermo‐mechanical response and survivability of key components of the collimating system (such as the collimating beam tube in the absorbers, the beam ...

Thermo-mechanical response of the halo intercepts interacting with the SNS proton beam

The integral part of the primary collimator of the SNS accumulator ring is a halo intercept assembly in the form of movable scraper blades that allow the interception of the halo protons in four planes. In order to achieve large Coulomb scattering of the halo protons and energy losses of less than 1%, platinum was chosen as the material of choice while its thickness was optimized to satisfy the energy loss requirements. This paper outlines the adopted design of the scraper assembly and presents the thermal response of the system that intercepts the beam halo as well as the subsequent thermal stress analysis and the issues associated with the performance of the scraper. Specifically, the current design incorporates a highly conducting material (copper) in the blade structure interfacing with the platinum scraper and is responsible for conducting the deposited energy away from the beam interception region. The mechanical performance and durability of such system, especially of the special bonding between the dissimilar materials, is the primary focus of this effort.