Book/Master Thesis

PUBDB-2022-01913

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Electron Temperature Measurements in Discharge Capillaries

Hörsch, J. M. (Corresponding author)DESY* ; Osterhoff, J. (Thesis advisor)DESY* ; Hillert, W. (Thesis advisor)CFEL*Extern*

2022
Verlag Deutsches Elektronen-Synchrotron DESY Hamburg

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Please use a persistent id in citations: doi:10.3204/PUBDB-2022-01913

Report No.: DESY-THESIS-2022-009

Abstract: The electron temperature of hydrogen and argon plasmas, that were produced at gas pressures of a few millibar and with electron densities in the range of $1\times10^{15} \text{cm}^{-3}$ to $1\times10^{17} \text{cm}^{-3}$, were investigated. These working points are typical of plasma sources which are used in beam-driven plasma wakefield accelerators such as FLASHForward. The particular plasmas were produced with a high voltage discharge inside a sapphire capillary that allowed, by means of their transparency, optical emission spectroscopy measurements. To determine the electron temperature emission lines were measured and the Boltzmann plot method, which requires optical thin emission lines and partial local thermodynamic equilibrium (pLTE), applied. These requirements were discussed and it was shown that the argon plasma is likely to exhibit stronger deviations than the hydrogen plasma. In hydrogen the maximum electron temperature could be successfully determined to $1.6\pm0.40 \text{eV}$ and this with significantly smaller uncertainties than in previous measurements. For argon this method was less successful and yielded un-physical results. This was in agreement with possibly stronger deviations from the pLTE conditions for argon and necessitated the implementation of a more complex collisional radiative model (CRM) for the temperature determination. The temperatures resulting from the CRM approach were similar to those obtained with the Boltzmann plot analysis and could therefore not improve the results. With these first results this study has laid the ground-work for the electron temperature characterisation in discharge capillaries for FLASHForward, which is a key for improving electron density measurements, plasma modelling and future active plasma lenses.

Note: Masterarbeit, Universität Hamburg, 2022

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Contributing Institute(s):

1. FTX Fachgruppe AST (HH_FH_FTX_AS)
2. Beam-Driven Plasma Accelerators (MPA2)
3. Data Analysis (XFEL_DO_DD_DA)

Research Program(s):

1. 621 - Accelerator Research and Development (POF4-621) (POF4-621)

Experiment(s):

1. FLASHForward

Appears in the scientific report 2022

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Database coverage:

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