Nuclear Commons^™

Structure Of Parton Quasi-Distributions And Their Moments, A. V. Radyushkin

Physics Faculty Publications

We discuss the structure of the parton quasi-distributions (quasi-PDFs) Q (y, P-3) outside the "canonical" -1 <= y <= 1 support region of the usual parton distribution functions (PDFs). Writing the y(n) moments of Q (y, P-3) in terms of the combined x(n-2l)k(perpendicular to)(2l)-moments of the transverse momentum distribution (TMD). F(x,k(perpendicular to)(2)), we establish a connection between the large-vertical bar y vertical bar behavior of Q (y, P-3) and large-k(perpendicular to)(2) behavior of F(x,k(perpendicular to)(2)). In particular, we show that the 1/k(perpendicular to)(2) hard tail of TMDs in QCD results in a slowly decreasing similar to 1/vertical bar y vertical bar behavior of quasi-PDFs for large vertical bar y vertical bar that produces infinite y(n) moments of Q(y, P-3). We also relate the - 1/vertical bar y vertical bar terms with the lnz(3)(2)-singularities of the Ioffe-time pseudo-distributions m(v, z(3)(2)). Converting the operator product expansion for m(v,z(3)(2)) into a matching relation between the quasi-PDF Q(y, P-3) and the light-cone PDF f (x, mu(2)), we demonstrate that there is no contradiction between the infinite values of the y(n) moments of Q (y, P-3) and finite values of the x(n) moments of f (x, mu(2))

First Results On Nucleon Resonance Photocouplings From The Γp → Π+Π−P Reaction, E. Golovatch, V. D. Burkert, D. S. Carman, R. W. Gothe, K. Hicks, M. J. Amaryan, M. Khachatryan, A. Klein, Y. Prok, Clas Collaboration

Physics Faculty Publications

We report the first experimental measurements of the nine 1-fold differential cross sections for the γ p → π⁺π⁻p reaction, obtained with the CLAS detector at Jefferson Laboratory. The measurements cover the invariant mass range of the final state hadrons from 1.6 GeV < W < 2.0 GeV. For the first time the photocouplings of all prominent nucleon resonances in this mass range have been extracted from this exclusive channel. Photoproduction of two charged pions is of particular importance for the evaluation of the photocouplings for the Δ (1620)1/2⁻, Δ (1700)3/2⁻, N(1720)3/2⁺, and Δ (1905)5/2⁺ resonances, which have dominant decays into the π π N final states rather than the more extensively studied single meson decay channels.

Polarization Analysis Of P̄ Produced In Pa Collisions, D. Grzonka, D. Alfs, A. Asaturyan, M. Carmignotto, M. Diermaier, W. Eyrich, B. Glowacz, F. Hauenstein, T. Horn, K. Kilian

Physics Faculty Publications

A quite simple procedure for the generation of a polarized antiproton beam could be worked out if antiprotons are produced with some polarization. In order to investigate this possibility measurements of the polarization of produced antiprotons have been started at a CERN/PS test beam. The polarization will be determined from the asymmetry of the elastic antiproton scattering at a liquid hydrogen target in the CNI region for which the analyzing power is well known. The data are under analysis and an additional measurement is done in 2018. Details on the experiment and the ongoing data analysis will be given.

Direct Observation Of Proton-Neutron Short-Range Correlation Dominance In Heavy Nuclei, M. Duer, A. Schmidt, J. R. Pybus, E. P. Segarra, A. Hrnjic, L. B. Weinstein, M. Hattawy, F. Hauenstein, S.E. Kuhn, Clas Collaboration

Physics Faculty Publications

We measured the triple coincidence A(e,e′n p) and A(e,e′ p p) reactions on carbon, aluminum, iron, and lead targets at Q² >1.5  (GeV/c)², x_B > 1.1 and missing momentum >400  MeV/c. This was the first direct measurement of both proton-proton (pp) and neutron-proton (np) short-range correlated (SRC) pair knockout from heavy asymmetric nuclei. For all measured nuclei, the average proton-proton (pp) to neutron-proton (np) reduced cross-section ratio is about 6%, in agreement with previous indirect measurements. Correcting for single-charge exchange effects decreased the SRC pairs ratio to ∼3%, which is lower than previous results. Comparisons to theoretical …

Instability Of Flux Flow And Production Of Vortex-Antivortex Pairs By Current-Driven Josephson Vortices In Layered Superconductors, Ahmad Sheikhzada, Alex Gurevich

Physics Faculty Publications

We report numerical simulations of the nonlinear dynamics of Josephson vortices driven by strong dc currents in layered superconductors. Dynamic equations for interlayer phase differences in a stack of coupled superconducting layers were solved to calculate a drag coefficient η(J) of the vortex as a function of the perpendicular dc current density J. It is shown that Cherenkov radiation produced by a moving vortex causes significant radiation drag increasing η(v) at high vortex velocities v and striking instabilities of driven Josephson vortices moving faster than a terminal v_c. The steady-state flux flow breaks down at ν > v …

First Measurement Of Near-Threshold J/ᴪ Exclusive Photoproduction Off The Proton, M. Ali, M. Amaryan, E.G. Anassontzis, Q. Zhou, X. Zhou, B. Zihlmann, Gluex Collaboration

Physics Faculty Publications

We report on the measurement of the γp -> J/ψp cross section from E_γ = 11.8 GeV down to the threshold at 8.2 GeV using a tagged photon beam with the GlueX experiment. We find that the total cross section falls toward the threshold less steeply than expected from two-gluon exchange models. The differential cross section dσ/dt has an exponential slope of 1.67 ± 0.39 GeV^-2 at 10.7 GeV average energy. The LHCb pentaquark candidates P⁺_c can be produced in the s channel of this reaction. We see no evidence for them and set model-dependent upper …

Form Factors Of Two-Hadron States From A Covariant Finite-Volume Formalism, Alessandro Baroni, Raúl Briceño, Maxwell T. Hansen, Felipe G. Ortega-Gama

Physics Faculty Publications

In this work we develop a Lorentz-covariant version of the previously derived formalism for relating finite-volume matrix elements to 2 + J → 2 transition amplitudes. We also give various details relevant for the implementation of this formalism in a realistic numerical lattice QCD calculation. Particular focus is given to the role of single-particle form factors in disentangling finite-volume effects from the triangle diagram that arise when J couples to one of the two hadrons. This also leads to a new finite-volume function, denoted G, the numerical evaluation of which is described in detail. As an example we discuss …

Conformal Invariance Of Transverse-Momentum Dependent Parton Distributions Rapidity Evolution, Ian Balitsky, Giovanni A. Chirilli

Physics Faculty Publications

We discuss conformal properties of TMD operators and present the result of the conformal rapidity evolution of TMD operators in the Sudakov region.

Can Long-Range Nuclear Properties Be Influenced By Short Range Interactions? A Chiral Dynamics Estimate, G. A. Miller, A. Beck, S. May-Tal Beck, L. B. Weinstein, E. Piasetzky, O. Hen

Physics Faculty Publications

Recent experiments and many-body calculations indicate that approximately 20% of the nucleons in medium and heavy nuclei (A ≥ 12) are part of short-range correlated (SRC) primarily neutron-proton (np) pairs. We find that using chiral dynamics to account for the formation of np pairs due to the effects of iterated and irreducible two-pion exchange leads to values consistent with the 20% level. We further apply chiral dynamics to study how these correlations influence the calculations of nuclear charge radii, that traditionally turncate their effect, to find that they are capable of introducing non-negligible effects.

Loi: Next Generation Tritium Experiments In Clas12, D. Gaskell, D. W. Higinbotham, D. Meekins, A. Ashkenazi, A. Denniston, R. Cruz-Torres, O. Hen, D. Nguyen, A. Papadopoulou, J. Pybus, A. Schmidt, E. P. Segarra, D. Dutta, Z. Ye, F. Hauenstein, M. Khachatryan, L. B. Weinstein, E. Piasetzky, S. Sirca, M. Mihovilovic, T. Kolar

Physics Faculty Publications

This LOI includes information on possible experiments for an experimental program using a new tritium target in CLAS12. It includes several pieces, including flavor tagged DIS on d, ³He, and ³H targets, and quasielatic scattering. A preliminary feasibility study indicates that a tritium target in Hall B is possible. We are submitting this LOI to get feedback from the PAC whether it is worth the effort of developing a full proposal, including significantly more work on the possible Hall B tritium target.

The bulk of the LOI discusses the flavor-tagged DIS measurement.

Compact -300 Kv Dc Inverted Insulator Photogun With Biased Anode And Alkali-Antimonide Photocathode, C. Hernandez-Garcia, P. Adderley, B. Bullard, J. Benesch, J. Grames, J. Gubeli, F. Hannon, J. Hansknecht, J. Jordan, R. Kazimi, G. A. Krafft, M. A. Mamun, M. Poelker, M. L. Stutzman, R. Suleiman, M. Tiefenback, Y. Wang, S. Zhang, H. Baumgart, G. Palacios-Serrano, S. Wijethunga, J. Yoskowitz, C. A. Valerio Lizarraga, R. Montoya Soto, A. Canales Ramos

Electrical & Computer Engineering Faculty Publications

This contribution describes the latest milestones of a multiyear program to build and operate a compact −300  kV dc high voltage photogun with inverted insulator geometry and alkali-antimonide photocathodes. Photocathode thermal emittance measurements and quantum efficiency charge lifetime measurements at average current up to 4.5 mA are presented, as well as an innovative implementation of ion generation and tracking simulations to explain the benefits of a biased anode to repel beam line ions from the anode-cathode gap, to dramatically improve the operating lifetime of the photogun and eliminate the occurrence of micro-arc discharges.

Determination Of The Magnetic Field Dependence Of The Surface Resistance Of Superconductors From Cavity Tests, J. R. Delayen, H. Park, S. Su. De Silva, G. Ciovati, Z. Li

Physics Faculty Publications

We present a general method to derive the magnetic field dependence of the surface resistance of superconductors from the Q-curves obtained during the cryogenic tests of cavities. The results are applied to coaxial half-wave cavities, TM-like “elliptical” accelerating cavities, and cavities of more complicated geometries.

Measurement Of Unpolarized And Polarized Cross Sections For Deeply Virtual Compton Scattering On The Proton At Jefferson Laboratory With Clas, N. Hirlinger Saylor, K. P. Adhikari, M. J. Amaryan, S. Bültmann, G. Gavalian, M. Khachatryan, A. Klein, S E. Kuhn, Y. Prok, J. Zhang, Z. W. Zhao, Clas Collaboration

Physics Faculty Publications

This paper reports the measurement of polarized and unpolarized cross sections for the ep → e 'p' γ reaction, which is composed of deeply virtual Compton scattering (DVCS) and Bethe-Heitler (BH) processes, at an electron beam energy of 5.88 GeV at the Thomas Jefferson National Accelerator Facility using the Large Acceptance Spectrometer CLAS. The unpolarized cross sections and polarized cross section differences have been measured over broad kinematics, 0.10 2 < 4.8 GeV²,and 0.09 < −t< 2.00 GeV². The results are found to be consistent with previous CLAS data, and these new data are discussed in the framework of the generalized parton distribution …

Short Range Correlations And The Isospin Dependence Of Nuclear Correlation Functions, R. Cruz-Torres, A. Schmidt, G. A. Miller, L. B. Weinstein, N. Barnea, R. Weiss, E. Piasetzky, O. Hen

Physics Faculty Publications

Pair densities and associated correlation functions provide a critical tool for introducing many-body correlations into a wide-range of effective theories. Ab initio calculations show that two-nucleon pairdensities exhibit strong spin and isospin dependence. However, such calculations are not available for all nuclei of current interest. We therefore provide a simple model, which involves combining the short and long separation distance behavior using a single blending function, to accurately describe the two nucleon correlations inherent in existing ab initio calculations. We show that the salient features of the correlation function arise from the features of the two-body short-range nuclear interaction, and …

Local Chiral Interactions, The Tritium Gamow-Teller Matrix Element, And The Three-Nucleon Contact Term, A. Baroni, R. Schiavilla, L. E. Marcucci, L. Girlanda, A. Kievsky, A. Lovato, S. Pastore, M. Piarulli, Steven C. Pieper, M. Viviani, R. B. Wiringa

Physics Faculty Publications

The Gamow-Teller (GT) matrix element contributing to tritium β decay is calculated with trinucleon wave functions obtained from hyperspherical-harmonics solutions of the Schrödinger equation with the chiral two- and three-nucleon interactions including Δ intermediate states that have recently been constructed in configuration space. Predictions up to next-to-next-to-next-to-leading order (N3LO) in the chiral expansion of the axial current (with Δ's) overestimate the empirical value by 1–4%. By exploiting the relation between the low-energy constant (LEC) in the contact three-nucleon interaction and two-body axial current, we provide new determinations of the LECs cD and cE that characterize this interaction by fitting the …

Beam-Target Helicity Asymmetry E In K 0 Λ And K 0 Σ 0 Photoproduction On The Neutron, D. H. Ho, R. A.. Schumacher, A. D' Angelo, A. Deur, J. Fleming, C. Hanretty, K. P. Adhikari, D. Adikaram, M. Khachatryan, A. Klein, M. Meyer, L. B. Weinstein, The Class Collaboration

Physics Faculty Publications

We report the first measurements of the E beam-target helicity asymmetry for the →γ→n→K⁰Λ and K⁰Σ⁰ channels in the energy range 1.70 ≤ W ≤ 2.34 GeV. The CLAS system at Jefferson Lab uses a circularly polarized photon beam and a target consisting of longitudinally polarized solid molecular hydrogen deuteride with low background contamination for the measurements. The multivariate analysis method boosted decision trees is used to isolate the reactions of interest. Comparisons with predictions from the KaonMAID, SAID, and Bonn-Gatchina models are presented. These results will help separate the isospin I=0 and I …

Electrostatic Design And Conditioning Of A Triple Point Junction Shield For A −200 Kv Dc High Voltage Photogun, G. Palacios-Serrano, F. Hannon, C. Hernandez-Garcia, M. Poelker, H. Baumgart

Electrical & Computer Engineering Faculty Publications

Nuclear physics experiments performed at the Continuous Electron Beam Accelerator Facility (CEBAF) at the Jefferson Lab require a DC high voltage photogun to generate polarized electron beams from GaAs photocathodes. The photogun uses a tapered ceramic insulator that extends into the vacuum chamber and mechanically holds the cathode electrode. Increasing the operating voltage from nominal −130 kV to −200 kV will provide lower beam emittance, better transmission through injector apertures, and improved photocathode lifetime. This desire to increase the photogun operating voltage led to the design of a triple-point-junction shield electrode which minimizes the electric field at the delicate insulator-metal-vacuum …

Asymmetric Relativistic Fermi Gas Model For Quasielastic Lepton-Nucleus Scattering, M. B. Barbaro, A. De Pace, T. W. Donnelly, J. A. Caballero, G. D. Megias, J. W. Van Orden

Physics Faculty Publications

We develop an asymmetric relativistic Fermi gas model for the study of the electroweak nuclear response in the quasielastic region. The model takes into account the differences between neutron and proton densities in asymmetric (N> Z) nuclei, as well as differences in the neutron and proton separation energies. We present numerical results for both neutral and charged-current processes, focusing on nuclei of interest for ongoing and future neutrino oscillation experiments. We point out some important differences with respect to the commonly employed symmetric Fermi gas model.

High-Brilliance, High-Flux Compact Inverse Compton Light Source, K. E. Deitrick, G. A. Krafft, B. Terzić, J. R. Delayen

Physics Faculty Publications

The Old Dominion University Compact Light Source (ODU CLS) design concept is presented-a compact Inverse Compton Light Source (ICLS) with flux and brilliance orders of magnitude beyond conventional laboratory-scale sources and greater than other compact ICLS designs. This concept utilizes the physics of inverse Compton scattering of an extremely low emittance electron beam by a laser pulse of rms length of approximately two-thirds of a picosecond (2/3 ps). The accelerator is composed of a superconducting radio frequency (SRF) reentrant gun followed by four double-spoke SRF cavities. After the linac are three quadrupole magnets to focus the electron beam to the …

First Measurement Of Ξ− Polarization In Photoproduction, J. Bono, L. Guo, K. P. Adhikari, M. J. Amaryan, G. Charles, G. Gavalian, M. Khachatryan, A. Klein, Y. Prok, J. Zhang, Z. W. Zhao

Physics Faculty Publications

Despite decades of studies of the photoproduction of hyperons, both their production mechanisms and their spectra of excited states are still largely unknown. While the parity-violating weak decay of hyperons offers a means of measuring their polarization, which could help discern their production mechanisms and identify their excitation spectra, no such study has been possible for doubly strange baryons in photoproduction, due to low production cross sections. However, by making use of the reaction γ p → K⁺K⁺Ξ−, we have measured, for the first time, the induced polarization, P, and the transferred polarization from circularly polarized …

Measurements Of The Γv P → P'Π+Π− Cross Section With The Clas Detector For 0.4 Gev2 < Q2 < 1.0 Gev2 And 1.3 Gev < W < 1.825 Gev, G. V. Fedotov, Iu. A. Skorodumina, V. D. Burkert, R. W. Gothe, G. Charles, M. Khachatryan, A. Klein, Y. Prok, Z. W. Zhao, Clas Collaboration

Physics Faculty Publications

New results on the single-differential and fully integrated cross sections for the process γ_vp → p'π+π− are presented. The experimental data were collected with the CLAS detector at Jefferson Laboratory. Measurements were carried out in the kinematic region of the reaction invariant mass W from 1.3 to 1.825 GeV and the photon virtuality Q² from 0.4 to 1.0 GeV². The cross sections were obtained in narrow Q² bins (0.05 GeV²) with the smallest statistical uncertainties achieved in double-pion electroproduction experiments to date. The results were found to be in agreement with previously …

Probing High-Momentum Protons And Neutrons In Neutron-Rich Nuclei, The Clas Collaboration, L. B. Weinstein, S. Bültmann, D. Bulumulla, G. Charles, G. Dodge, F. Hauenstein, C. E. Hyde, A. Klein, S. Nadeeshani, Y. Prok, Z. W. Zhao

Physics Faculty Publications

The atomic nucleus is one of the densest and most complex quantum-mechanical systems in nature. Nuclei account for nearly all the mass of the visible Universe. The properties of individual nucleons (protons and neutrons) in nuclei can be probed by scattering a high-energy particle from the nucleus and detecting this particle after it scatters, often also detecting an additional knocked-out proton. Analysis of electron- and proton-scattering experiments suggests that some nucleons in nuclei form close-proximity neutron–proton pairs with high nucleon momentum, greater than the nuclear Fermi momentum. However, how excess neutrons in neutron-rich nuclei form such close-proximity pairs remains unclear. …

First Measurement Of The Ti(E, É) X Cross Section At Jefferson Lab, Jefferson Lab Hall A Collaboration, F. Hauenstein, C. Hyde

Physics Faculty Publications

To probeCPviolation in the leptonic sector usingGeVenergy neutrino beams in current and future experiments using argon detectors, precise models of the complex underlying neutrino and antineutrino interactions are needed. The E12-14-012 experiment at JeffersonLab HallAwas designed to perform a combined analysis of inclusive and exclusive electron scatterings on both argon (N = 22) and titanium (Z = 22) nuclei using GeV-energy electron beams. Themeasurement on titanium nucleus provides essential information to understand the neutrino scattering on argon, large contribution to which comes from scattering off neutrons. Here we report the first experimental study of electron-titanium scattering as double-differential cross section …

Differential Cross Section For Γ D →Ωd Using Clas At Jefferson Lab, T. Chetry, K. Hicks, N. Compton, S. Adhikari, J. Ball, G. Charles, M. Khachatryan, Y. Prok, L. B. Weinstein, Z. W. Zhao

Physics Faculty Publications

The cross section for coherent ω-meson photoproduction off the deuteron has been measured for the first time as a function of the momentum transfer t=(P_γ−P_ω)² and photon energy E_γ using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The cross sections are measured in the energy range 1.4 γ<3.4 GeV. A model based on ω−N rescattering is consistent with the data at low and intermediate momentum transfer, |t|. For 2.8 γ<3.4 GeV, the total cross-section of ω−N scattering, based on fits within the framework of the Vector Meson Dominance model, is in the range of 30–40 mb.

Ion Bunch Formation Strategies For The Jleic Collider, Bamunuvita Randika Prasad Gamage

Physics Theses & Dissertations

An Electron-Ion Collider (EIC) has been proposed and supported as the next major nuclear physics facility in the United States, with very high design luminosities of 10³³ − 10³⁴ cm⁻² s⁻¹. The Jefferson Lab EIC concept, JLEIC, includes construction of a new ion beam accelerator complex. To achieve the required luminosity, the JLEIC ion collider requires unprecedentedly short ion bunches of 1 cm length at a high repetition frequency of 476 MHZ. However, only much longer ion bunches are formed by the ion injector complex producing beams for the collider ring. Formation of short ion …

Hard Exclusive Pion Electroproduction At Backward Angles With Clas, K. Park, M. Guidal, R. W. Gothe, B. Pire, G. Charles, C. E. Hyde, S E. Kuhn, J. Poudel, Y. Prok

Physics Faculty Publications

We report on the first measurement of cross sections for exclusive deeply virtual pion electroproduction off the proton, ep → e'nπ⁺, above the resonance region at backward pion center-of-mass angles. The ϕ∗ π-dependent cross sections were measured, from which we extracted three combinations of structure functions of the proton. Our results are compatible with calculations based on nucleon-to-pion transition distribution amplitudes (TDAs). These non-perturbative objects are defined as matrix elements of threequark-light-cone-operators and characterize partonic correlations with a particular emphasis on baryon charge distribution inside a nucleon.

Nucleon And Nuclear Structure Through Dilepton Production, I. V. Anikin, N. Baltzell, M. Boer, R. Boussarie, V. M. Braun, S. J. Brodsky, A. Camsonne, W. C. Chang, L. Colaneri, C. E. Hyde

Physics Faculty Publications

Transverse momentum distributions and generalized parton distributions provide a comprehensive framework for the three-dimensional imaging of the nucleon and the nucleus experimentally using deeply virtual semi-exclusive and exclusive processes. The advent of combined high luminosity facilities and large acceptance detector capabilities enables experimental investigation of the partonic structure of hadrons with time-like virtual probes, in complement to the rich on-going space-like virtual probe program. The merits and benefits of the dilepton production channel for nuclear structure studies are discussed within the context of the International Workshop on Nucleon and Nuclear Structure through Dilepton Production taking place at the European Center …

Light-Nuclei Spectra From Chiral Dynamics, M. Piarulli, A. Baroni, L. Girlanda, A. Kievsky, A. Lovato, Ewing Lusk, L. E. Marcucci, Steven C. Pieper, R. Schiavilla, M, Viviani, R. B. Wiringa

Physics Faculty Publications

In recent years local chiral interactions have been derived and implemented in quantum Monte Carlo methods in order to test to what extent the chiral effective field theory framework impacts our knowledge of few- and many-body systems. In this Letter, we present Green's function Monte Carlo calculations of light nuclei based on the family of local two-body interactions presented by our group in a previous paper in conjunction with chiral three-body interactions fitted to bound- and scattering-state observables in the three-nucleon sector. These interactions include Δ intermediate states in their two-pion-exchange components. We obtain predictions for the energy levels and …

Double K-S(0) Photoproduction Off The Proton At Clas, S. Chandavar, J. T. Goetz, K. Hicks, D. Keller, M. C. Kunkel, M. Paolone, D. P. Weygand, K. P. Adhikari, S. Adhikari, Z. Akbar, G. Charles, G. Gavalian, M. Khachatryan, A. Klein, Y. Prok, J. Zhang, Z. W. Zhao, The Clas Collaboration

Physics Faculty Publications

The f₀(1500) meson resonance is one of several contenders to have significant mixing with the lightest glueball. This resonance is well established from several previous experiments. Here we present the first photoproduction data for the f₀(1500) via decay into the K-S(0) K-S(0) channel using the CLAS detector. The reaction γp → f_Jp → K-S(0) K-S(0) p,where J = 0,2, was measured with photon energies from 2.7–5.1 GeV. A clear peak is seen at 1500 MeV in the background subtracted invariant mass spectra of the two kaons. This is enhanced if the measured four-momentum transfer …

300 Kv Dc High Voltage Photogun With Inverted Insulator Geometry And Csk₂Sb Photocathode, Y.W. Wang, P.A. Adderley, J. F. Benesch, D.B. Bullard, J.M. Grames, F. E. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, Geoffrey A. Krafft, M. A. Mamun, G. G. Palacios Serrano, M. Poelker, R. Suleiman, M. G. Tiefenback, S.A.K. Wijethunga

Physics Faculty Publications

A compact DC high voltage photogun with inverted-insulator geometry was designed, built and operated reliably at 300 kV bias voltage using alkali-antimonide photocathodes. This presentation describes key electrostatic design features of the photogun with accompanying emittance measurements obtained across the entire photocathode surface that speak to field non-uniformity within the cathode/anode gap. A summary of initial photocathode lifetime measurements at beam currents up to 4.5 mA is also presented.