Enhancement of Photoemission on P-type GaAs using Surface Acoustic Waves

We demonstrate that photoemission properties of GaAs photocathodes (PCs) can be altered by surface acoustic waves (SAWs) generated on the PC surface due to dynamical piezoelectric fields of SAWs. Simulations with COMSOL indicate that electron effective lifetime in p-doped GaAs may increase by a factor of 10x to 20x. It implies a significant, by a factor of 2x to 3x, increase of quantum efficiency (QE) for GaAs PCs. Essential steps in device fabrication are demonstrated, including deposition of an additional layer of ZnO for piezoelectric effect enhancement, measurements of I-V characteristic of the SAW device, and ability to survive high-temperature annealing.Comment: 5 pages, 4 figure

Final Technical Report on STTR Project DE-FG02-04ER86191 Hydrogen Cryostat for Muon Beam Cooling

The project was to develop cryostat designs that could be used for muon beam cooling channels where hydrogen would circulate through refrigerators and the beam-cooling channel to simultaneously refrigerate 1) high-temperature-superconductor (HTS) magnet coils, 2) cold copper RF cavities, and 3) the hydrogen that is heated by the muon beam. In an application where a large amount of hydrogen is naturally present because it is the optimum ionization cooling material, it was reasonable to explore its use with HTS magnets and cold, but not superconducting, RF cavities. In this project we developed computer programs for simulations and analysis and conducted experimental programs to examine the parameters and technological limitations of the materials and designs of Helical Cooling Channel (HCC) components (magnet conductor, RF cavities, absorber windows, heat transport, energy absorber, and refrigerant).The project showed that although a hydrogen cryostat is not the optimum solution for muon ionization cooling channels, the studies of the cooling channel components that define the cryostat requirements led to fundamental advances. In particular, two new lines of promising development were opened up, regarding very high field HTS magnets and the HS concept, that have led to new proposals and funded projects

Ionization Cooling using Parametric Resonances

Ionization Cooling using Parametric Resonances was an SBIR project begun in July 2004 and ended in January 2008 with Muons, Inc., (Dr. Rolland Johnson, PI), and Thomas Jefferson National Accelerator Facility (JLab) (Dr. Yaroslav Derbenev, Subcontract PI). The project was to develop the theory and simulations of Parametric-resonance Ionization Cooling (PIC) so that it could be used to provide the extra transverse cooling needed for muon colliders in order to relax the requirements on the proton driver, reduce the site boundary radiation, and provide a better environment for experiments. During the course of the project, the theoretical understanding of PIC was developed and a final exposition is ready for publication. Workshops were sponsored by Muons, Inc. in May and September of 2007 that were devoted to the PIC technique. One outcome of the workshops was the interesting and somewhat unexpected realization that the beam emittances using the PIC technique can get small enough that space charge forces can be important. A parallel effort to develop our G4beamline simulation program to include space charge effects was initiated to address this problem. A method of compensating for chromatic aberrations by employing synchrotron motion was developed and simulated. A method of compensating for spherical aberrations using beamline symmetry was also developed and simulated. Different optics designs have been developed using the OptiM program in preparation for applying our G4beamline simulation program, which contains all the power of the Geant4 toolkit. However, no PIC channel design that has been developed has had the desired cooling performance when subjected to the complete G4beamline simulation program. This is believed to be the consequence of the difficulties of correcting the aberrations associated with the naturally large beam angles and beam sizes of the PIC method that are exacerbated by the fringe fields of the rather complicated channel designs that have been attempted. That is, while the designs developed and tested using the matrix program OptiM can work well, a real simulation with lumped dipoles, quadrupoles, and solenoids and their associated fringe fields has not succeeded. As a consequence of this realization, a new approach is being attempted that is based on the use of a helical solenoid (HS) channel that is made of simple coils that provide a much more homogeneous magnetic field. However, in order to use the HS a new approach was required to generate a variable dispersion that is needed according to the PIC theory described above. This approach and its first implementation will be described at EPAC08 in June, 2008

Muon Acceleration in a Superconducting Proton Linac *

Abstract This note describes how a future Fermilab proton driver [1] based on TESLA superconducting linac modules can perform as both the source of protons to produce the muons and as the accelerator of the muons to be used for a neutrino factory or muon collider. Recent advances in muon cooling Introduction Fermilab has conducted design studies and cost estimates for both an 8 GeV synchrotron and an 8 GeV superconducting Linac as possible replacements for the Booster synchrotron, which now serves as the injector to the Fermilab Main Injector (FMI) and as the source of neutrinos for the MINIBOONE experiment. The recent decision to concentrate on cold technology for the International Linear Collider (ILC) has added an additional argument for the Booster replacement to be based on superconducting technology. The large number of muons needed for a collider, or for a muon storage ring to produce neutrinos, requires a high-intensity proton driver for π-production, a highacceptance π−µ decay channel, a µ-cooling system, a rapid acceleration system and a high-luminosity collider ring or muon storage ring with long straight decay or interaction region sections. Presently, the baseline design for the acceleration system assumes a high-gradient straight linac followed by several FFAG rings. In this paper the concept of a Neutrino Factory based on a highgradient proton Linac that is also used for acceleration of muons will be presented. We beleive that the incremental cost to upgrade the superconducting proton driver linac to be able to accelerate muons, including the costs to produce and cool the muons, will be considerably less than the costs estimated in previous neutrino factory design studies. We also believe that such an approach can produce a much higher neutrino flux and, because of the necessity for effective muon cooling, also be on the path to an energy frontier muon collider

A search for direct muon production in the forward direction

We propose to search for direct muon production in the forward direction from 300 GeV protons incident on a heavy nuclear target. By using the first stage of the Ml beam as a source of a diffracted proton beam and the second and third stages of Ml as a spectrometer, one can make a measurement of the direct muon to pion ratio at values of x between 0.3 and 0.75. If this ratio is on the order of 10{sup -4}, the event rates are on the order of 800 direct muons/hr. at an x of .5. The modifications to the Ml beam are minor

The Case for a Muon Collider Higgs Factory

We propose the construction of a compact Muon Collider Higgs Factory. Such a machine can produce up to \sim 14,000 at 8\times 10^{31} cm^-2 sec^-1 clean Higgs events per year, enabling the most precise possible measurement of the mass, width and Higgs-Yukawa coupling constants.Comment: Supporting letter for the document: "Muon Collider Higgs Factory for Smowmass 2013", A White Paper submitted to the 2013 U.S. Community Summer Study of the Division of Particles and Fields of the American Physical Society, Y. Alexahin, et. al, FERMILAB-CONF-13-245-T (July, 2013

Superconducting helical solenoid systems for muon cooling experiment at Fermilab

Novel configurations of superconducting magnet system for Muon Beam Cooling Experiment is under design at Fermilab. The magnet system has to generate longitudinal and transverse dipole and quadrupole helical magnetic fields providing a muon beam motion along helical orbit. It was found that such complicated field configuration can be formed by a set of circular coils shifted in transverse directions in such a way that their centers lay on the center of the helical beam orbit. Closed beam orbit configurations were also proposed and investigated. This paper describes the magnetic and mechanical designs and parameters of such magnetic system based on a NbTi Rutherford type cable. The helical solenoid fabrication, assembly and quench protection issues are presented

The role of Comprehension in Requirements and Implications for Use Case Descriptions

Within requirements engineering it is generally accepted that in writing specifications (or indeed any requirements phase document), one attempts to produce an artefact which will be simple to comprehend for the user. That is, whether the document is intended for customers to validate requirements, or engineers to understand what the design must deliver, comprehension is an important goal for the author. Indeed, advice on producing ‘readable’ or ‘understandable’ documents is often included in courses on requirements engineering. However, few researchers, particularly within the software engineering domain, have attempted either to define or to understand the nature of comprehension and it’s implications for guidance on the production of quality requirements. Therefore, this paper examines thoroughly the nature of textual comprehension, drawing heavily from research in discourse process, and suggests some implications for requirements (and other) software documentation. In essence, we find that the guidance on writing requirements, often prevalent within software engineering, may be based upon assumptions which are an oversimplification of the nature of comprehension. Hence, the paper examines guidelines which have been proposed, in this case for use case descriptions, and the extent to which they agree with discourse process theory; before suggesting refinements to the guidelines which attempt to utilise lessons learned from our richer understanding of the underlying discourse process theory. For example, we suggest subtly different sets of writing guidelines for the different tasks of requirements, specification and design

Disordered Eating among Preadolescent Boys and Girls: The Relationship with Child and Maternal Variables

Objective: (i) To analyze the eating behaviors and body satisfaction of boys and girls and to examine their mothers’ perceptions of these two domains; and (ii) to evaluate eating problem predictors using child body mass index (BMI), self-esteem, and body satisfaction as well as maternal BMI, eating problems, and satisfaction with their child’s body. The participants included 111 children (54.1% girls aged between 9 and 12 years old) and their mothers. Assessment measures included the Child Eating Attitude Test, the Self-Perception Profile for Children, the Eating Disorders Questionnaire, and the Child Eating Behavior Questionnaire. Child and maternal measures also included BMI and Collins Figure Drawings. Results: (i) No association between child and maternal BMI for either sex was found; (ii) no difference was found between boys and girls with regard to eating behavior; (iii) most children revealed a preference for an ideal body image over their actual body image; (iv) most mothers preferred thinner bodies for their children; (v) greater BMI was related to higher body dissatisfaction; and (vi) child BMI and dissatisfaction with body image predicted eating disturbances in boys, whereas self-esteem, maternal BMI, and eating behavior predicted them in girls. Discussion: Maternal eating problems and BMI were related to female eating problems only