59063827
Emittance Measurement Techniques used in the 1 MeV RFQ for the PET Isotope Linac at Fermilab
Beam emittance measurements have been performed on the {sup 3}He{sup +} beam at the PET isotope production accelerator, being commissioned at Fermilab for the Biomedical Research Foundation in Shreveport, Louisiana, USA. Emittances have been measured at injection to and extraction from the first RFQ, at 20 keV and 1 MeV, respectively. A single slit followed by a 48 electrode collector is used in the standard way to measure the divergence of the {sup 3}He{sup +} beam as a function of position. Noise reduction operations have been developed, both in hardware and software. These techniques and the emittance measurement results are presented.
113925183
Factors Affecting H- Beam Performance in the Fermilab Linac
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>>
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.
14890549
Lattice QCD at finite density
I discuss different approaches to finite density lattice QCD. In particular, I focus on the structure of the phase diagram and discuss attempts to determine the location of the critical end-point. Recent results on the transition line as function of the chemical potential (T{sub c}({mu}{sub q})) are reviewed. Along the transition line, hadronic fluctuations have been calculated; which can be used to characterize properties of the Quark Gluon plasma and eventually can also help to identify the location of the critical end-point in the QCD phase diagram on the lattice and in heavy ion experiments. Furthermore, I comment on the structure of the phase diagram at large {mu}{sub q}.
15351369
Charm production in deep inelastic scattering from threshold to high Q2
Charm final states in deep inelastic scattering constitute ~ 25% of the inclusive cross-section at small x as measured at HERA. These data can reveal important information on the charm and gluon structure of the nucleon if they are interpreted in a consistent perturbative QCD framework which is valid over the entire energy range from threshold to the high energy limit. We describe in detail how this can be carried out order-by-order in PQCD in the generalized MSbar formalism of Collins (generally known as the ACOT approach), and demonstrate the inherent smooth transition from the 3-flavor to the 4-flavor scheme in a complete order αs calculation, using a Monte Carlo implementation of this formalism. This calculation is accurate to the same order as the conventional NLO F2 calculation in the limit Q/mc >> 1. It includes the resummed large logarithm contributions of the 3-flavor scheme (generally known in this context as the fixed-flavor-number or FFN scheme) to all orders of αsln (mc2/Q2). For the inclusive structure function, comparison with recent HERA data and the existing FFN calculation reveals that the relatively simple order-αs (NLO) 4-flavor (mc≠0) calculation can, in practice, be extended to rather low energy scales, yielding good agreement with data over the full measured Q2 range. The Monte Carlo implementation also allows the calculation of differential distributions with relevant kinematic cuts. Comparisons with available HERA data show qualitative agreement; however, they also indicate the need to extend the calculation to the next order to obtain better description of the differential distributions.
16115905
Flavor and quark mass dependence of QCD thermodynamics
We calculate the transition temperature in 2 and 3-flavor QCD using improved gauge and staggered fermion actions on lattices with temporal extent Nτ = 4. We find Tc = 173 (8) MeV and 154 (8) MeV for nf = 2 and 3, respectively. In the case of 3-flavor QCD we present evidence that the chiral critical point, i.e. the second order endpoint of the line of first order chiral phase transitions, belongs to the universality class of the 3d 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-
14462382
The Infrared behavior of QCD cross-sections at next-to-next-to leading order
In this talk we examine how one-loop soft and collinear splitting functions occur in the calculation of next-to-next-to-leading order (NNLO) corrections to production rates, and we present the one-loop gluon soft and splitting functions, computed to all orders in the dimensional regularization parameter ǫ. We apply the one-loop gluon soft function to the calculation of the next-to-leading logarithmic corrections to the Lipatov vertex to all orders in ǫ.