4567819
Influence of Growth Method on K3Sb Photocathode Structure and Performance
A combination of material science techniques is used to determine the influence of the growth parameters on structure and performance of photocathode materials. In-situ x-ray diffraction (XRD) and in-situ grazing incidence small angle x-ray scattering (GiSAXS), as well as after growth xray reflectivity (XRR) and�/2� - XRD measurements were performed at synchrotron radiation sources. K3Sb is a precursor material for the preparation of CsK2Sb and Na2KSb. The materials growth was studied intensively to optimize this intermediate growth step in terms of quantum efficiency and roughness. The results of two growth methods, a “layer by layer” type and a “super-lattice type”, are presented, as well as the interaction of the K3Sb phase with Cesium.
86859005
Instrumentation for Theory-Inspired Photocathode Development within the Large Area Picosecond Photodetector (LAPPD) Project
Abstract We have designed and are commissioning a laboratory for the growth and characterization of photocathodes at Argonne National Laboratory. Two growth facilities, a versatile ultra high vacuum growth chamber and an industrial photomultiplier production facility, allow the investigation of fundamental aspects of the cathode growth and the development, modification and implementation of recipes in an industrial production environment. The instrumentation allows the study of optical properties, electrical behaviors and spectral response of the cathode.
118071326
High Performance Photocathodes based on Molecular Beam Epitaxy Deposition for Next Generation Photo Detectors and Light Sources
The development of high-performance photocathodes is a key challenge for future accelerator and particle physics applications. In this paper photocathode growth through molecular beam epitaxy is introduced as a promising technique to obtain robust, highly efficient alkali-antimonide based photocathodes. Recent research shows that the quantum efficiency of photocathodes can be significantly enhanced through control of the photocathode crystallinity. Molecular beam epitaxy allows for cost-effective growth of large-area photocathodes with excellent control of the stoichiometry and crystallinity, making photocathodes with peak quantum efficiencies exceeding 35% routine.
55912862
Alkali Antimonide Photocathodes in a Can
The next generation of x-ray light sources will need reliable, high quantum efficiency photocathodes. These cathodes will likely be from the alkali antimonide family, which currently holds the record for highest average current achieved from a photoinjector. In this work, we explore a new option for delivering these cathodes to a machine which requires them: use of sealed commercial vacuum tubes. Several sealed tubes have been introduced into a vacuum system and separated from their housing, exposing the active photocathode on a transport arm suitable for insertion into an injector. The separation was achieved without large loss of QE. These cathodes have been compared to those grown via traditional methods, both in terms of QE and in terms of crystalline structure, and found to be similar.
85558439
Development of an Alkali Transfer Photocathode for Large Area Microchannel Plate-Based Photodetectors
The goal of the Large Area Picosecond Photodetector collaboration is to produce 8-inch by 8-inch microchannel plate-based photodetectors, with fast timing resolution of the order of 1-100 ps and high spatial resolution of 0.1-10 mm. At Argonne, the transfer photocathode process being developed is based on a recipe for manufacturing photomultiplier cathodes. Starting with a commercial PMT fabrication facility, the photocathode recipe and growth system will be scaled up using a custom-built glass vessel to produce transfer photocathodes. This leads to the production of the 8-inch by 8-inch photocathode that will be incorporated with the photodetector assembly system.
119296586
Dynamically generated hadron resonances
As an example of dynamically generated resonances we mention the interaction of vector mesons with baryons within the local hidden gauge formalism which gives rise to a large amount of such states, many of which can be associated to known resonances, while others represent predictions for new resonances. The width of these states coming from decay into pseudoscalar baryon is also addressed. We also mention recent states coming from ρπ interaction obtained with Faddeev equations.
119096553
The role of $N^*(2120)$ nucleon resonance in $K\Lambda(1520)$ photon and hadronic productions
The associate KΛ(1520) photon and hadronic production in the γp → K+Λ(1520), pp → pK+Λ(1520) and π-p → K0Λ(1520) reactions are investigated within the effective Lagrangian approach and the isobar model. We are interested in the contribution from the N*(2120) (previously called N*(2080)) resonance, which has a significant coupling to the KΛ(1520) channel. The theoretical results show that the current experimental data for the γp → K+Λ(1520) reaction favor the existence of the N*(2120) resonance, and that these measurements can be used to further constrain its properties. We present results, including the N*(2120) contribution, for total cross sections of the γp → K+Λ(1520), π-p → K0Λ(1520), and pp → pK+Λ(1520) reactions. For this latter one, we also calculate invariant mass and Dalitz plot distributions.
62797135
Faddeev fixed center approximation to the $N\bar{K}K$ system and the signature of a $N^*(1920)(1/2^+)$ state
We perform a calculation for the three-body NK-barK scattering amplitude by using the fixed-center approximation to the Faddeev equations, taking the interaction between N and K-bar, N and K, and K-bar and K from the chiral unitary approach. The resonant structures show up in the modulus squared of the three-body scattering amplitude and suggest that a NK-barK hadron state can be formed. Our results are in agreement with others obtained in previous theoretical works, which claim a new N* resonance around 1920 MeV with spin-parity J{sup P}=1/2{sup +}. The existence of these previous works allows us to test the accuracy of the fixed center approximation in the present problem and sets the grounds for possible application in similar problems, as an explorative tool to determine bound or quasibound three-hadron systems.
116935217
N*(1920)(1/2+) STATE IN THE $NK\bar{K}$ SYSTEM
We study the three body system by using the fixed center approximation to the Faddeev equations, taking the interaction between N and , N and K, and and K from the chiral unitary approach. Our results suggest that a hadron state, with spin-parity JP = 1/2+, and mass around 1920 MeV, can be formed.
119217176
Nucleon resonances in the $\pi^- p \to K^0 \Lambda$ reaction near threshold
We investigate the two-body reaction $\pi^- p \to K^{0} \Lambda$ within the effective Lagrangian approach and the isobar model. In addition to the "background" contributions from $t$-channel $K^*$ exchange, $u$-channel $\Sigma(1192)$ and $\Sigma^*(1385)$ exchanges, and $s$-channel nucleon pole terms, the contributions from the nucleon resonances $N^*(1535)$, $N^*(1650)$, and $N^*(1720)$ are investigated. It is shown that the inclusion of these nucleon resonances contributions leads to a good description of the experimental total and differential cross sections data at low energy region. The $s$-channel $N^*(1535)$, $N^*(1650)$, and $N^*(1720)$ resonances and the $t$-channel $K^*$ exchange give the dominant contributions below $W = 1.76$ GeV, while the $u$-channel $\Sigma(1192)$ and $\Sigma^*(1385)$ exchanges give the minor contributions.