107827345
Proposed FNAL 750 KeV Linac Injector Upgrade
The present FNAL linac H{sup -} injector has been operational since 1978 and consists of a magnetron H{sup -} source and a 750 keV Cockcroft-Walton Accelerator. The proposed upgrade to this injector is to replace the present magnetron source having a rectangular aperture with a circular aperture, and to replace the Cockcroft-Walton with a 200 MHz RFQ. Operational experience at other laboratories has shown that the upgraded source and RFQ will be more reliable and require less manpower than the present system.
123613871
Observations of the transverse and longitudinal nature of the Fermilab linac beam
The installation of nonintercepting beam position monitors (BPMs) in the 200 MeV linac at Fermilab has facilitated several new observations on the character of the linac beam. In particular, two interesting phenomena have been discovered: a high-frequency change in the beam position and a slow variation in the phase-lock loops during a 30 mu s beam pulse. Progress in initiating the Delta -t measurement is being made. The Delta -t procedure adjusts the RF phase and amplitude in each of the accelerating modules of a linac. The procedure uses beam-induced signals from linac BPMs to determine changes in the times of flight of beam bunches when the tuned module is turned off and when it is turned on.<<ETX>>
113925183
Factors Affecting H- Beam Performance in the Fermilab Linac
118674965
Operation and improvements of the Fermilab 400 MeV Linac
The 400 MeV Fermilab Linac Upgrade commissioning began August 28, 1993. High energy physics collider operation (run 1b) began in November 1993 and ended March 1, 1996. The Linac, operating at 98% reliability, provided 400 MeV H{sup -} beam to the Booster and 66 MeV H{sup -} beam to the Neutron Therapy Facility. During this time, the beam intensity, which initially was administratively set to 35 MA, rose to a peak of 50 mA while losses decreased significantly. This paper discusses the Linac operation and reliability since the Upgrade.
119968235
Direct current surface plasma source with high emission current density
A surface plasma source for long-time dc operation with efficient production of negative ions and high emission current density has been designed and tested. Several modifications of the discharge system, beam extraction, cesium supply, and source design have been tested for long-time operation. The emission current density of H− ions has been increased to j=1 A/cm2 in the dc mode of operation with a discharge voltage, Ud=80 V; a discharge current, Id=0.9 A and a discharge power, P=70 W. Corresponding efficiency of the current density production S=j/P=15 A/cm2 kW is much higher than in modern positive ion sources. Source features determining an operational lifetime will be discussed.
121242219
Attainment of an MeV-range, DC electron beam for the Fermilab cooler
To prepare a beam generation device for Fermilab's future Recycler Electron Cooling system, an experimental set-up with a simplified beam line has been commissioned at Fermilab. Stable operation was achieved at an electron energy of 3.5 MeV and a DC beam current of up to 0.5 A. The main reason for interruptions of the operation was found to be microsecond long bursts of the cathode current. While the frequency of the interruptions is determined primarily by a flow of secondary ions, the resulting reduction in the duty factor depends on the beam optics, the protection systems, and the tube electric field strength.
119495100
QCD phenomenology of charm production at HERA
We compare different schemes for the treatment of heavy quark production in Deep-Inelastic Scattering (DIS). For fully-integrated quantities such as F{sub 2}(x,Q{sup 2}), we advocate the use of the General-Massive Variable-Flavor-Number (GM-VFN) scheme; we present some results showing the progress of a Next-to-Leading Order calculation in this scheme. For differential quantities, the Fixed-Flavor-Number (FFN) scheme provides a more appropriate starting point. We present a new calculation of the azimuthal distribution of charm quark production in DIS. All results have been obtained using a Monte Carlo program under development.
119202385
Equation of state at non-zero baryon density based on lattice QCD
We employ the lattice QCD data on Taylor expansion coefficients to extend our previous parametrization of the equation of state to finite baryon density. When we take into account lattice spacing and quark mass dependence of the hadron masses, the Taylor coefficients at low temperature are equal to those of hadron resonance gas. Parametrized lattice equation of state can thus be smoothly connected to the hadron resonance gas equation of state at low temperatures.
119331939
Chiral perturbation theory for lattice QCD with a twisted mass term
Quantum chromodynamics on a lattice with Wilson fermions and a chirally twisted mass term for two degenerate quark flavours is considered in the framework of chiral perturbation theory. The pion mass and decay constant are calculated in next-to-leading order including terms linear in the lattice spacing a.
118579706
The strange degrees of freedom in QCD at high temperature
We discuss recent results on fluctuations of conserved charges, and their approach to the hadron resonance gas at temperatures below the chiral crossover (Tc) as well as to a gas of free quarks at very high temperatures. We will focus on the strange degrees of freedom and verify that they are consistent with those of an uncorrelated gas of hadrons for temperatures of T . 160 MeV and that they can be described by a quasi particle model at best for T & 2Tc. To extract this information we use all cumulants of net baryon number and net strangeness fluctuations and their correlations up to the fourth order. In particular we propose observables that serve as indicator for the validity of the hadronic degrees of freedom and show that the partial pressures from different strangeness sectors agree separately with HRG model predicions.
125171654
Lattice QCD thermodynamic results with improved staggered fermions
We present results on the QCD equation of state, obtained with two different improved dynamical staggered fermion actions and almost physical quark masses. Lattice cut-off effects are discussed in detail as results for three different lattice spacings are available now, i.e. results have been obtained on lattices with temporal extent of Nτ=4,6 and 8. Furthermore we discuss the Taylor expansion approach to non-zero baryon chemical potential and present the isentropic equation of state on lines of constant entropy per baryon number.