Inverted Geometry Photo-Electron Gun Research and Development at TU Darmstadt

Herbert, Maximilian; Enders, J.; Fritzsche, Yuliya; Kurichiyanil, Neeraj; Wende, Vincent

doi:10.18429/jacow-ipac2018-thpmk101

Cited by 3 publications

(3 citation statements)

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“…Additionally, (iv) a transportable UHV chamber is constructed to store and transfer the cleaned photocathode samples. Not discussed in this manuscript, is a chamber being set up with an inverted-insulator high-voltage DC electrode in which activated cathodes will be placed for long-term tests and dedicated experiments [21,22]. The system will also be augmented by a sixth UHV chamber in which cooling a high-voltage electrode near the photocathode is foreseen to minimize the residual-gas pressure for an extended lifetime [23].…”

Section: Photocathode Preparation Systemmentioning

confidence: 99%

A test system for optimizing quantum efficiency and dark lifetime of GaAs photocathodes

et al. 2019

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Gallium-arsenide-based photocathodes are used for a variety of applications, including electron-beam production for particle accelerators. An ultra-high vacuum teststand has been developed for cleaning and preparation of photocathodes. First studies using the apparatus were carried out investigating quantum efficiency and vacuum (dark) lifetimes of GaAs photcathodes that were prepared using different procedures involving Cs, Li, and O 2 . While the two-stage activation procedure with Cs and O 2 yielded the highest quantum efficiency of up to (25.9 ± 1.3) % at wavelength 405 nm, the vacuum lifetime of cathodes activated with Cs, Li, and O 2 using a two-stage process exceeded those obtained in single-stage process by more than a factor of three.

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Section: Photocathode Preparation Systemmentioning

confidence: 99%

A test system for optimizing quantum efficiency and dark lifetime of GaAs photocathodes

et al. 2019

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“…Its Spin-Polarized Injector (SPIn) features a DC electron gun operating with GaAs photocathodes [10]. Additionally, a separate dedicated test stand for Photo-Cathode Activation, Testing, and Cleaning using atomic Hydrogen (Photo-CATCH) is available for research on gun development and photocathode activation independent of beamtime at the S-DALINAC [11,12]. It features a chamber for photocathode activation as well as a 60 kV DC photo-gun with adjacent diagnostics beamline.…”

Section: Introductionmentioning

confidence: 99%

Automated Activation Procedure for GaAs Photocathodes at Photo-CATCH*

Herbert¹,

Eggert²,

Enders³

et al. 2023

Proceedings of 19th Workshop on Polarized Sources, Targets and Polarimetry — PoS(PSTP2022)

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Photo-electron sources using GaAs-based photocathodes are used to provide high-brightness and high-current beams of (spin-polarized) electrons for accelerator applications such as free-electron lasers (FELs) and energy recovery linacs (ERLs). Such cathodes require a thin surface layer to achieve negative electron affinity (NEA) for photoemission. The layer is deposited during an activation procedure that greatly influences the resulting quantum efficiency of the photocathode and robustness of the layer. To standardize this process, the automatization of the activation procedure is investigated for operational use in an accelerator. This contribution presents first proof-of-principle studies of a basic automated activation procedure at TU Darmstadt's EPICS-controlled photocathode test stand Photo-CATCH. Using a co-deposition scheme with Cs and O 2 , several automated activations have been performed. Eight out of nine consecutive automated activations were successful, yielding a mean quantum efficiency of (4.9 ± 0.8) %, corresponding to a factor of 0.8 ± 0.2 relative to manual operation, and reproducibility to within ±15 %.

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“…At TU Darmstadt, a test facility for Photo-Cathode Activation, Test, and Cleaning using atomic-Hydrogen, Photo-CATCH, which is also dedicated to DC photoelectron gun research and development, has been established recently [16]. It uses an axisymmetric IIGG, featuring a two-part electrode consisting of a main electrode body and an extendable lift for photocathode loading [17]. An upgrade from −60 kV to −300 kV bias voltage has been envisioned and is currently under development.…”

Section: Introductionmentioning

confidence: 99%

Freeform shape optimization of a compact DC photo-electron gun using isogeometric analysis

Förster,

Schöps,

Enders

et al. 2020

Preprint

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Compact DC high-voltage photo-electron guns are able to meet the challenging demands of highcurrent applications such as energy-recovery linacs. A main design parameter for such sources is the electric field strength, which depends on the electrode geometry and is limited by the field-emission threshold of the electrode material. In order to minimize the maximum field strength for optimal gun operation, isogeometric analysis (IGA) can be used to exploit the axisymmetric geometry and describe its cross section by non-uniform rational B-splines, the control points of which are the parameters to be optimized. This computationally efficient method is capable of describing CADgenerated geometries using open source software (GeoPDEs, NLopt, Octave) and it can simplify the step from design to simulation. We will present the mathematical formulation, the software workflow and the results of an IGA-based shape optimization for a planned high-voltage upgrade of the DC photogun teststand Photo-CATCH at TU Darmstadt. Simulations assuming a bias voltage of −300 kV yielded maximum field gradients of 9.06 MV m −1 on the surface of an inverted-insulator electrode and below 3 MV m −1 on the surface of the photocathode.

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Inverted Geometry Photo-Electron Gun Research and Development at TU Darmstadt

Cited by 3 publications

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A test system for optimizing quantum efficiency and dark lifetime of GaAs photocathodes

A test system for optimizing quantum efficiency and dark lifetime of GaAs photocathodes

Automated Activation Procedure for GaAs Photocathodes at Photo-CATCH*

Freeform shape optimization of a compact DC photo-electron gun using isogeometric analysis

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