117849086
Fermilab Linac 1997-98 operations, studies and improvements
The Fermilab Linac operated as an injector for the Tevatron Fixed Target Program, booster studies and as a neutron source for cancer treatment during 1997 and 1998. Operational reliability was 98% of the scheduled operating time. Beam currents were generally in the 45 to 48 mA range with a high of 52 mA during studies. After completion of the Fixed Target Program, the Linac embarked on a series of studies. The studies were intended to verify visual survey data indicating a misalignment of the low energy linac, correct the misalignment, and install and use new wires for determining emittance. Operations data and studies results will be presented.
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.
113925183
Factors Affecting H- Beam Performance in the Fermilab Linac
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>>
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.
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.
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.
8018207
Top Quark Physics at the NLC
A high energy $e^+e^-$ linear collider (NLC) is an excellent tool for studying the properties of the top quark. In this talk I review some of the theory of top quark production and decay in $e^+e^-$ collisions both at threshold and in the continuum. I also report on the results of phenomenological analyses of $t\bar t$ production at the NLC.
13969763
Baryon number strangeness and electric charge fluctuations at zero and non-zero chemical potential
We present results on baryon number, strangeness and electric charge fluctuations in QCD at non-zero density and temperature obtained from lattice calculations with almost physical quark masses. At vanishing chemical potential, i.e. under conditions almost realized at RHIC and the LHC, quartic fluctuations of net baryon number and strangeness are large in a narrow temperature interval characterizing the transition region from the low to the high temperature phase. Our results are based on Taylor expansions in light and strange quark chemical potentials, i.e. we rigorously compute corrections to bulk thermodynamic quantities at non-vanishing chemical potential, by performing a Taylor expansion in μ/T. We find non-monotonic behavior for the radius of convergence of this series, which could be a hint for a critical end point in the (T, μ)-plane.
53607643
Intrinsic Charm Parton Distribution Functions from CTEQ-TEA Global Analysis
Sayipjamal Dulat, 2, ∗ Tie-Jiun Hou, Jun Gao, Joey Huston, Jon Pumplin, Carl Schmidt, Daniel Stump, and C.–P. Yuan † 1 School of Physics Science and Technology, Xinjiang University, Urumqi, Xinjiang 830046 China 2 Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 U.S.A. 3 Institute of Physics, Academia Sinica, Taipei, Taiwan 115 4 Department of Physics, Southern Methodist University, Dallas, TX 75275-0181, U.S.A.
15858058
Non-zero density QCD by the Taylor expansion method: The isentropic equation of state, hadronic fluctuations and more
We discuss the Taylor expansion approach to non-zero baryon chemical potential ($\mu_B$) and present results on expanion coefficients of the pressure and energy density up to the 6-th order in $\mu_B$. Calculations have been performed with (2+1)-flavor of improved staggerd fermions (p4fat3) and almost physical masses on lattices with temporal extent of four and six time slices. We use the expansion coefficients to construct the isentropic equation of state on lines of constant entropy per baryon number and various different hadronic fluctuations. Furthermore, we estimate the radius of convegence of our expansion, which can be seen as a method to analyze the structure of the QCD phase diagram.