Status and recent developments at the polarized-electron injector of the superconducting Darmstadt electron linear accelerator S-DALINAC

Poltoratska, Y.; Eckardt, C.; Ackermann, Wolfgang; Aulenbacher, K.; Bahlo, Thore; Barday, R.; Brunken, M.; Burandt, Christoph; Eichhorn, Ralf; Enders, J.; Espig, Martin; Franke, Sylvain Sebastian; Ingenhaag, C.; Lindemann, J.; Müller, Wolfgang; Platz, Markus; Roth, Markus; Schneider, F.; Wagner, Max; Weber, A.; Weiland, Thomas; Zwicker, B.

doi:10.1088/1742-6596/298/1/012002

Cited by 11 publications

(7 citation statements)

References 7 publications

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“…Similarly, we observe normalized transverse rms emittances of x = 0.108 mm mrad and y = 0.194 mm mrad. This is a good match compared to the values measured at operating photo-electron guns [9,10]. An rms energy spread of ∆E rms = 48.4 eV is observed at the chamber exit for a field strength of 2.99 MV m −1 on the photocathode surface at −300 kV bias voltage, compared to 84 eV with 2.5 MV m −1 at −200 kV, as reported in [55].…”

Section: B Particle Tracking Resultssupporting

confidence: 86%

“…However, a high bias voltage is desired to provide sufficient initial acceleration for the beam and to minimize emittance in spite of space-charge effects. Since common negative bias voltages of state-of-the-art DC photo-electron guns are in the range of −100 kV to −500 kV [8][9][10][11], the combination of * peter.foerster@cem.temf.de such high voltages with a suitable electrode geometry and material poses a great challenge for the design of compact guns. The decisive limiting factor is the field emission threshold of the electrode material, imposing a maximum electric field strength on the geometric design.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: B Particle Tracking Resultssupporting

confidence: 86%

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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show abstract

“…Email address: g.weber@gsi.de (G. Weber) During the last two years, such polarimeters were applied in a series of polarization-resolved bremsstrahlung measurements that have been carried out at the teststand of the polarized electron source SPIN [13,14] at the Technical University of Darmstadt. In these experiments the polarization transfer was studied in collisions of polarized electrons with gold foils of about 100 µg/cm 2 thickness and at an impact energy of 100 keV [15,16].…”

Section: Introductionmentioning

confidence: 99%

PEBSI – A Monte Carlo simulator for bremsstrahlung arising from electrons colliding with thin solid-state targets

Weber¹,

Märtin²,

Surzhykov³

et al. 2012

Nuclear Instruments and Methods in Physics Research Section B:

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We present a Monte Carlo code dedicated to the simulation of bremsstrahlung arising in collisions of polarized electrons with thin target foils. The program consists of an electron transport algorithm taking into account elastic electron-nucleus scattering and inelastic collisions with target electrons as well as a treatment of polarized-electron bremsstrahlung emission. Good agreement is found between the predictions of the electron transport code and data stemming from other simulation programs and experiments. In addition, we present first results from the bremsstrahlung simulation which indicate a significant decrease in the degree of linear polarization of bremsstrahlung even for the thinnest gold targets considered.

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“…Comparably, albeit at a smaller scale, a dedicated test stand for DC photo-gun research and development, Photo-CATCH, with a 60 kV photo-gun and 60 keV beamline has been constructed at the Institut für Kernphysik of the Technische Universität Darmstadt. It provides an environment for research and development to optimize the existing DC photo-gun, which is located at the Spin-Polarized Injector SPIn of the in-house electron accelerator S-DALINAC [11][12][13]. A collaboration between the two institutes has been established in order to effectively capitalize on our joint area of research.…”

Section: Introductionmentioning

confidence: 99%

Lifetime Measurements of GaAs photocathodes at the Upgraded Injector Test Facility at Jefferson Lab*

Herbert¹,

Enders²,

Poelker³

et al. 2020

Proceedings of the 18th International Workshop on Polarized Sources, Targets, and Polarimetry — PoS(PSTP2019)

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Photo-cathodes based on GaAs can be used in photo-electron sources to supply spin-polarized, high-current electron beams for various applications. An activation, adding a thin surface layer, is needed to achieve negative electron affinity (NEA) for such cathodes. Typically, Cs is used in combination with an oxidant. Previous studies have suggested that the addition of Li to this process can increase the quantum efficiency η of the cathode as well as the lifetime τ of the cathode surface layer, both crucial parameters for photo-electron source operation. Charge lifetime studies of bulk GaAs photo-cathodes activated with Cs, NF 3 , and Li have been conducted using the photo-electron gun of the Upgraded Injector Test Facility (UITF) at the Thomas Jefferson National Accelerator Facility (JLab), extracting beam currents of up to 100 µA. Evidence for significant charge lifetime enhancement with Li in the activation process is found.

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Status and recent developments at the polarized-electron injector of the superconducting Darmstadt electron linear accelerator S-DALINAC

Cited by 11 publications

References 7 publications

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

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

PEBSI – A Monte Carlo simulator for bremsstrahlung arising from electrons colliding with thin solid-state targets

Lifetime Measurements of GaAs photocathodes at the Upgraded Injector Test Facility at Jefferson Lab*

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