67749273
Commissioning and first operational experience of the 400 MeV Linac at Fermilab
Commissioning of the Fermilab High Energy Linac during September and October of 1993 has increased the energy of the H- linac from 200 to 400 MeV. The Linac Upgrade is one portion of the Fermilab Upgrad and is intended to reduce the incoherent space-charge tuneshift at injection into the 8 GeV Booster. To accomplish this increase in energy within the existing enclosure, four 201.25 MHz drift-tube linac tankshave been replaced by seven 805 MHz side-coupled cavity modules to accelerate the beam from 116 MeV to 400 MeV. Each module is driven with a klystron amplifier delivering 10 MW of peak power for 60 {mu}sec with a maximum pulse repetition rate of 15 Hz. Nominal beam current is 35 mA with a pulselength of 40 {mu}sec. Results from commissioning and operational experience during Fermilab Collider Run 1B are presented.
113925183
Factors Affecting H- Beam Performance in the Fermilab Linac
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.
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.
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>>
5511493
Common features of deconfining and chiral critical points in QCD and the three state Potts model in an external field
In the presented study we investigated the second order endpoints of the lines of first order phase transitions which emerge for the QCD in the heavy and light quark mass regime and for the three-dimensional three state Potts model with an external field. We located the endpoints with Binder cumulants and constructed the energy-like and ordering-field-like observables. The joint probability distributions of these scaling fields and the values of the Binder cumulant confirm that all three endpoints belong to the universality class of the 3-dimensional Ising model.
859441
A Monte Carlo Solution to the BFKL Equation
A simple solution to the BFKL equation is obtained as a series in the number of real gluons emitted with transverse momentum greater than some small cutoff μ. This solution reveals physics inside the BFKL ladder which is hidden in the standard inclusive solution, and lends itself to a straightforward Monte Carlo implementation. With this approach one can explore new useful physical observables, which are shown to be independent of the cutoff μ. In addition, this approach allows the imposition of kinematic constraints (such as energy conservation) which are important at finite energies. The distribution of ∑ E⊥ of particles in a central rapidity bin between two widely-spaced jets is presented as an example. The BFKL (Balitsky-Fadin-Kuraev-Lipatov) equation [1], which systematically resums powers of αs times large rapidity intervals or logarithms of Feynman x in perturbative QCD, has recently moved from the purely theoretical realm to the phenomenological arena. The classic prediction of the BFKL resummation is the rise of F2(x) at small x in deep inelastic scattering. Unfortunately, due to the resiliency of the parton density functions and DGLAP [2] evolution equations, this observation [3, 4] is still open to interpretation [5]. Alternatively, by tagging jets on both ends of a large rapidity interval, as suggested by Mueller and Navalet [6], it is possible to unambiguously isolate the effects of the BFKL ladder from the parton density functions. Predictions of this kind include the rise in the cross section as a function of the rapidity interval, both in hadron-hadron [6] and leptonhadron colliders [7]. In particular, recent preliminary results from H1 [3] on deep inelastic scattering with a tagged jet at fixed xj show an intriguing rise in the cross section with decreasing xBJ that is not well-explained either by a fixed-order matrix element calculation [8] or by parton shower Monte Carlo simulations. The BFKL prediction [9], however, seems to be in good agreement. Other observables related to the kinematics of the tagging jets, such as the decorrelation in azimuthal angle [10], have also been considered. With the advent of BFKL phenomenology, it has become a necessity to understand the range of validity and the errors inherent in the BFKL approximations. The calculation of the next-to-leading logarithmic (NLL) corrections to the BFKL matrix elements is currently under way [11]. Short of these full NLL corrections, it has been shown in [12] that some of the largest corrections to the asymptotic the-
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.
18184787
QCD THERMODYNAMICS WITH ALMOST REALISTIC QUARK MASSES.
Ongoing calculations on the QCDOC supercomputer at Brookhaven National Laboratory and the APEnext installation at the University of Bielefeld aim to determine the critical temperature of the QCD phase transition as well as the equation of state with almost realistic quark masses. We will discuss preliminary results of the quark mass and cut-off dependence of order parameters, susceptibilities, static quark potentials and the critical temperature in (2+1)-flavor QCD. All these quantities are of immediate interest for heavy ion phenomenology.
13413480
The chiral critical point in 3-flavour QCD
Abstract We determine the second order endpoint of the line of first order phase transitions, which occur in the light quark mass regime of 3-flavour QCD at finite temperature, and analyze universal properties of this chiral critical point. A detailed analysis of Binder cumulants and the joint probability distributions of energy like and ordering-field like observables confirms that the chiral critical point belongs to the universality class of the three-dimensional Ising model. From a calculation with improved gauge and staggered fermion actions we estimate that the transition is first order for pseudo-scalar meson masses less than about 200 MeV.