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arXiv2011

Measurement of magnetic permeability of steel laminations of Booster gradient magnets

New experiments at Fermilab require higher beam intensities at Booster, resulting in higher influence of magnet steel on the beam. In order to carefully take these effects into account it is necessary to know geometric and material properties of magnets. This work is dedicated to the measurement of magnetic permeability of steel laminations of Booster gradient magnets as a complex function of frequency in the frequency range from several megahertz up to 1 GHz. The magnetic permeability is estimated by analyzing S-parameters of microstrip lines made up from laminated steel.

physics.acc-ph↗
arXiv2012

On Quantum Integrable Systems

Many quantum integrable systems are obtained using an accelerator physics technique known as Ermakov (or normalized variables) transformation. This technique was used to create classical nonlinear integrable lattices for accelerators and nonlinear integrable plasma traps. Now, all classical results are carried over to a nonrelativistic quantum case.

quant-ph↗
arXiv2011

Observation of Relativistic Electrons Deflection by a Bunch Coulomb Field

According to the E.L. Feinberg viewpoint on the possibility of a semi-bare electron state we may expect a state of electron with non-equilibrium Coulomb field during the time range of {γ^2 λ/c}, where γ is the Lorents-factor of electron, c is light velocity and λ is the wavelength corresponding to a frequency in Fourier expansion of the Coulomb field of relativistic electron. If this non-equilibrium Coulomb field has a spatial asymmetry, a relativistic electron may be deflected by its own Coulomb field. For the {γ^2 λ/c=1m} we may observe this effect in macroscopic mode when the electrons are grouped in bunches with the population Ne=10^8. We present in this paper the experimental observation of the deflection of an electron beam by an asymmetrical non-equilibrium Coulomb field of electron bunch. The experiment was performed on the relativistic electron beam of the microtron of Tomsk Polytechnic University.

physics.acc-ph↗
arXiv2012

Proceedings of EuCARD-AccNet-EuroLumi Workshop: The High-Energy Large Hadron Collider, Malta, Republic of Malta, 14 - 16 Oct 2010

This report contains the proceedings of the EuCARD-AccNet-EuroLumi Workshop on a High-Energy Large Hadron Collider 'HE-LHC10' which was held on Malta from 14 to 16 October 2010. This is the first workshop where the possibility of building a 33 TeV centre-of-mass energy proton-proton accelerator in the LHC tunnel is discussed. The key element of such a machine will be the 20 T magnets needed to bend the particle beams: therefore much space was given to discussions about magnet technologies for high fields. The workshop also discussed possible parameter sets, issues related to beam dynamics and synchrotron radiation handling, and the need for new injectors, possibly with 1 TeV energy. The workshop searched for synergies with other projects and studies around the world facing similar challenges or pushing related technologies, revisited past experience, and explored a possible re-use of existing superconducting magnets. Last not least, it reinforced the inter-laboratory collaborations within EuCARD, especially between CERN and its European, US, and Japanese partners.

physics.acc-ph↗
arXiv2012

A 233 km Circumference Tunnel for $e^+$$e^-$, $p$$\bar {p}$, and $μ^{+} μ^{-}$ Colliders

In 2001 a cost analysis survey was conducted to build a 233km circumference tunnel in northern Illinois in which to build a Very Large Hadron Collider. Ten years later I have reexamined the proposal, taking into consideration the technological advancements in all the aspects of construction cost analysis. I outline the implementations of $e^+ e^-$, $p{\bar{p}}$, and $μ^+μ^-$ collider rings in the tunnel using 21${\rm{st}}$ century technology. The $e^+e^-$ collider employs a Crab Waist Crossing, ultra low emittance damped bunches, 12 GV of superconducting RF, and 0.026 Tesla low coercivity grain oriented silicon steel/concrete dipoles. The $p{\bar{p}}$ collider uses the high intensity Fermilab $\bar{p}$ source, exploits high cross sections for $p\bar{p}$ production of high mass states, and uses 2 Tesla ultra low carbon steel/YBCO superconductor magnets run with liquid neon. The $μ^+μ^-$ ring ramps the $p{\bar{p}}$ magnets at 8 Hz every 0.4 seconds, uses 250 GV of SRF, and mitigates neutrino radiation with a phase shifting roller coaster FODO lattice. Such colliders could provide the means necessary for Chicago, and more importantly America, to stay relevant and competitive in the international marketplace of particle physics.

physics.acc-ph↗
arXiv2012

Shielding Studies for Superconducting RF Cavities at Fermilab

A semi-empirical method that allows us to predict intensity of generated field emission in superconducting RF cavities is described. Spatial, angular and energy distributions of the generated radiation are calculated with the FISHPACT code. The Monte Carlo code MARS15 is used for modeling the radiation transport in matter. A comparison with dose rate measurements performed in the Fermilab Vertical Test Facility for ILC-type cavities with accelerating gradients up to 35 MV/m is presented as well.

physics.acc-ph↗
arXiv2012

First high gradient test results of a dressed 325 MHz superconducting single spoke resonator at Fermilab

A new superconducting RF cavity test facility has been commissioned at Fermilab in conjunction with first tests of a 325 MHz, β = 0.22 superconducting single-spoke cavity dressed with a helium jacket and prototype tuner. The facility is described and results of full gradient, CW cavity tests with a high Qext drive coupler are reported. Sensitivities to Q disease and externally applied magnetic fields were investigated. Results are compared to bare cavity results obtained prior to hydrogen degassing and welding into the helium jacket.

physics.acc-ph↗
arXiv2012

A Model for One-Dimensional Coherent Synchrotron Radiation including Short-Range Effects

A new model is presented for simulating coherent synchrotron radiation (CSR) in one dimension. The method is based on convolving an integrated Green function (IGF) with the longitudinal charge density. Since it is based on an IGF, the accuracy of this approach is determined by how well one resolves the charge density and not by resolving the single particle wake function. Since short-range wakefield effects are included analytically, the approach can be much more efficient than ordinary (non-IGF) approaches in situations where the wake function and charge density have disparate spatial scales. Two cases are presented: one derived from the full wake including short-range effects, and one derived from the asymptotic wake. In the latter case the algorithm contains the same physics as others based on the asymptotic approximation, but requires only the line charge density and not its derivative. Examples are presented that illustrate the limitations of the asymptotic-wake approximation, and that illustrate how microbunching can increase the CSR fields by orders of magnitude depending on the microbunching wavelength.

physics.acc-ph↗
arXiv2012

Status of Hybrid Target R&D at KEK LINAC

A hybrid positron source, consisting of a crystal as electron to photon converter and a amorphous target, is a candidate to relax heat load problem for high intensity positron sources. In this article we report status of experimental study using the 8 GeV electron beam at KEKB LINAC.

physics.acc-ph↗
arXiv2012

Temperature Profile Measurements During Heat Treatment of BSCCO 2212 Coils

The temperature profile of two different BSCCO 2212 coils has been analyzed. The profiles are obtained from thermocouples imbedded in the windings during the heat treatment that activates the 2212. The melting and freezing of the 2212 is clearly observed. A model that describes the data and can be used to guide the processing of new coils has been developed.

physics.acc-ph↗
arXiv2012

Shielding Experiments Under JASMIN Collaboration at Fermilab(IV) - Measurement and Analyses of High-Energy Neutron Spectra in the Anti-Proton Target Station

Neutron spectra in high-energy region between 1 and 100-MeV in the shield configuration of the anti-proton target station and a 120-GeV proton beam at Fermi National Accelerator Laboratory (Fermilab) were determined using the reaction rate data obtained with the multi-foil activation method. Two kinds of methods were employed for the determination of neutron spectra: one is the fitting method which is newly developed in this work, another is the unfolding method with SAND-II code. The calculations were performed using the PHITS. From the comparison between the calculated and experimental neutron spectra, it concluded that the PHITS can be used for shielding design of high-energy proton accelerators.

physics.acc-ph↗
arXiv2012

Dark Current Studies for SwissFEL

Activation of the surroundings of an accelerator must be quantified and those data provided to the official agencies. This is a necessary step in obtaining the authorization to operate such an accelerator. SwissFEL, being a fourth generation light source, will produce more accelerated charges, which are dumped or lost, than conventional third generation light source, such as the Swiss Light Source. We have simulated the propagation of a dark current beam produced in the photoelectron gun using tracking codes like ASTRA and Elegant for the current layout of SwissFEL. Experimental studies have been carried out at the SwissFEL test facilities at PSI (C-Band RF Stand and SwissFEL Injector Test Facility), in order to provide necessary input data for detailed study of components (RF gun and C-band RF structures) using the simulation code OPAL. A summary of these studies are presented.

physics.acc-ph↗
arXiv2012

Target Studies for the Production of Lithium8 for Neutrino Physics Using a Low Energy Cyclotron

Lithium 8 is a short lived beta emitter producing a high energy anti-neutrino, which is very suitable for making several measurements of fundamental quantities. It is proposed to produce Lithium 8 with a commercially available 60 MeV cyclotron using protons or alpha particles on a Beryllium 9 target. We have used the GEANT4 program to model these processes, and calculate the anti-neutrino fluxes that could be obtained in a practical system. We also calculate the production of undesirable contaminants such as Boron 8, and show that these can be reduced to a very low level.

physics.acc-ph↗
arXiv2013

Effects of Nonlinear Decoherence on Halo Formation

High intensity proton linacs and storage rings are central for the development of advanced neutron sources, extending the intensity frontier in high energy physics, as drivers for the production of pions in neutrino factories or muon colliders, and for the transmutation of radioactive waste. Such high intensity beams are not attainable using conventional linear lattices. It has been shown in the single particle limit that integrable nonlinear lattices permit much larger tune spreads than conventional linear lattices, which would mitigate many of the space charge restrictions that limit intensity. In this paper, we present numerical studies of space charge effects on a trial nonlinear lattice with intense bunches. We observe that these nonlinear lattices and their accompanying tune spreads strongly mitigate halo formation using a result from the particle-core model known to cause halo formation in linear lattices.

physics.acc-ph↗
arXiv2014

Femtosecond Time-resolved MeV Electron Diffraction

We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminum and single-crystal 1T-TaS2 are obtained utilizing a 5 femto-Coulomb (~3x10^4 electrons) pulse of electrons at 2.8 MeV. The high quality of the electron diffraction patterns confirm that electron beam has a normalized emittance of ~50 nm-rad. The corresponding transverse and longitudinal coherence length are ~11 nm and ~2.5 nm, respectively. The timing jitter between the pump laser and probe electron beam was found to be ~ 100 fs (rms). The temporal resolution is demonstrated by observing the evolution of Bragg and superlattice peaks of 1T-TaS2 following an 800 nm optical pump and was found to be 130 fs. Our results demonstrate the advantages of MeV electron diffraction: such as longer coherent lengths, large scattering cross-section and larger signal-to-noise ratio, and the feasibility of ultimately realizing 10 fs time-resolved electron diffraction.

physics.ins-det↗
arXiv2013

Compact narrow-band THz radiation source based on photocathode rf gun

Narrow-band THz coherent Cherenkov radiation can be driven by a subpicosecond electron bunch traveling along the axis of a hollow cylindrical dielectric-lined waveguide. We present a scheme of compact THz radiation source based on the photocathode rf gun. On the basis of our analytic result, the subpicosecond electron bunch with high charge (800pC) can be generated directly in the photocathode rf gun. A narrow emission spectrum peaked at 0.24 THz with 2 megawatt (MW) peak power is expected to gain in the proposed scheme (the length of the facility is about 1.2 m), according to the analytical and simulated results.

physics.acc-ph↗
arXiv2013

Fast Laser Cooling of Long Lived Ion Beams

Some peculiarities of fast laser cooling of long-lived ion beams in storage rings are discussed. Selective interaction of ions and broadband laser beam with sharp frequency and geometric edges is used while laser and ion beams are partially overlapped. The rates of change of the ion beam density in different regions of the phase space and at different moments of time in this scheme of cooling differ. That is why the generalized Robinson theorem valid for the infinitesimal phase space regions of non exponential cooling in turn is used to interpret the results.

physics.acc-ph↗