Session S12: Accelerator Physics

Proton Linac Front End for High Intensity Neutrino Source at Fermilab

Fermilab has recently proposed the construction of an 8 GeV superconducting linac for the exploration of the high intensity frontier. The High Intensity Neutrino Source (HINS) R{\&}D program was established to explore the feasibility of certain technical solutions proposed for the front end of a high intensity linac. The low energy ($\sim $60 MeV) section operates at 325 MHz and comprises an RFQ, two re-buncher cavities, 16 room temperature (RT) and 29 superconducting cross-bar H-type resonators, and superconducting solenoid focusing elements. One of the distinguishing features of this linac is the use of one klystron to feed multiple radio frequency (RF) elements. As an example, the RFQ, the re-bunchers and the 16 RT cavities are powered by a single 2.5 MW pulsed klystron. To achieve individual control over the phase and the voltage amplitude, each of the RF elements is equipped with a high power vector modulator. The RF control system will be discussed. The first RT cavity is completed with a power coupler, two mechanical tuners, vacuum and cooling systems, and has been RF conditioned. Preliminary tests on resonance frequency stability control and tests results of the cavity resonance frequency response to cooling water temperature and tuner position will also be discussed.   

Experimental verification of predicted oscillations near a spin resonance

The Chao matrix formalism allows analytic calculations of a beam's polarization behavior inside a spin resonance. We recently tested its prediction of polarization oscillations occurring in a stored beam of polarized particles near a spin resonance. Using a 1.85 GeV/c polarized deuteron beam stored in COSY, we swept a new rf solenoid's frequency rather rapidly through 400 Hz during 100 ms, while varying the distance between the sweep's end frequency and the central frequency of an rf-induced spin resonance. Our measurements of the deuteron's polarization near and inside the resonance agree with the Chao formalism's predicted oscillations.   

RF spin resonance strength for stored polarized deuterons.

We studied the ratio of the measured to predicted rf spin resonance strengths $\varepsilon _{FS}$/$^{\ast }\varepsilon _{Bdl}$ for an rf dipole and an rf solenoid using 1.85 GeV/c vertically polarized deuterons at COSY. We measured $\varepsilon _{FS}$ by fitting spin-flipping data to the Froissart-Stora equation, and we calculated each $^{\ast }\varepsilon _{Bdl}$ from each rf magnet's $\smallint $\textit{Bdl.} We found no dependence on the beam's momentum spread or the rf frequency sweep range for either the rf dipole or solenoid. We saw an enhancement of $\varepsilon _{FS}$/$^{\ast }\varepsilon _{Bdl}$ near a 1$^{st}$-order intrinsic resonance for the rf dipole, but no enhancement for the rf solenoid. Except near the intrinsic resonance, the deuteron's $\varepsilon _{FS}$ was very near $^{\ast }\varepsilon _{Bdl}$ for the rf solenoid, but was about 7 times smaller than $^{\ast }\varepsilon _{Bdl }$ for the rf dipole. (Supported by the German BMBF Science Ministry.)   

High Power Proton Beams Genrated with the Z-Petawatt Laser

The Z-Petawatt laser system has been built up in stages over the last few years. It has been used to generate and characterize ion beam emission from solid density targets. These experiments addressed radiography and energy deposition on secondary targets, partly to be applied at the Z-Accelerator facility at Sandia National Laboratories as the capabilities of Z-Petawatt evolve. Cu, Al, Pd and Au targets were used for Target-Normal-Sheath- Acceleration of protons and heavier ions. Results from parametric studies on target edge emission will be presented along with experiments on ballistic and magnetic proton beam focusing.   

Proton and ion beams generated with a CO2 laser

The proton- and ion generation experiment is initiated at the BNL's ATF where thin-foil targets are irradiated by a 1-TW, picosecond CO2 laser. A particle beam is produced in the normal direction to the foil's rare surface. A spectrometer equipped with CR-39 dosimetry plates reveals proton- and ion spectra in the sub-MeV energy range. Comparison with results of previous experiments that used solid-state lasers allows for verification of wavelength scaling of the ion- and proton laser acceleration. We present simulations that lead the way toward further up-scaling of proton beam energy and luminocity in order to answer the demand for compact proton sources and injectors for scientific, medical and industrial applications.   

New Concepts and Fermilab Facilities for Antimatter Research

There has long been significant interest in continuing antimatter research at the Fermi National Accelerator Laboratory. Beam kinetic energies ranging from 10 GeV all the way down to the eV scale and below are of interest. There are three physics missions currently being developed: the continuation of charmonium physics utilizing an internal target; atomic physics with in-flight generated antihydrogen atoms; and deceleration to thermal energies and paasage of antiprotons through a grating system to determine their gravitation acceleration. Non-physics missions include the study of medical applications, tests of deep-space propulsion concepts, low-risk testing of nuclear fuel elements, and active interrogation for smuggled nuclear materials in support of homeland security. This paper reviews recent beam physics and accelerator technology innovations in the development of methods and new Fermilab facilities for the above missions.