IES Calibration Modeling Phil Valek and Roman Gomez May 29, 2013

Outline Summary of testing Recent Modeling and Analysis Results Remaining Work

IES in Calibration Chamber

Calibration notes Calibration performed over 3 different time periods, with the last occurring as part of a refurbishment – Oct 1999 – Sept 2001 – July 2003 (15 keV and 2 keV) Calibration perform primarily with positive ions and some tests with negative ions Records of most of the facility states (i.e. incident beam flux) have been lost – Beam position and energy information is known

Overall Goals Use a pre-existing SIMION simulation model to determine transmission characteristics of the IES electron ESA Compare simulation and calibration results to arrive at reasonable Geometric Factor (G) values for all 16 azimuth anodes Apply these findings to in-flight instrument data (forthcoming)

Simulation Technique: Reverse-fly Particles are started from the detector and flown out of the ESA Position, angle, energy, and velocity values are recorded for particles exiting the analyzer Particle trajectories are reversed (velocity vectors in particular) and the inverted quantities are used to determine the ESA transmission characteristics

Simulation Geometry Acquired from Greg Miller Rotated for ease of simulating Electron ESA 1:1 dimensional correspondence with flight model SIMION model includes potential arrays for individual ESA plates, detectors and deflection electrodes All potential array are programmatically adjustable Side View: Electron ESA Bottom IES: Iso-view

Electron ESA Ion ESA Electron DEF Ion DEF

IonDef: 0 V ElecDef: 0V

Reverse Fly of IES Four Energies Chosen: eV, eV, eV, and eV. Preliminary: Particles gridded in energy, angles, and position systematically flown from the detector to define the edges of the ESA’s transmission envelope Once found, the limiting trajectories are used to “bracket” the values of a randomized distribution at the detector. Transmission envelope at eV shown in three views: ESA Voltage = V Side View Top View Edge-on View

Flyback Checks Side View Top View Edge-on View Edge-on View w/2500 V on MCP eV Flyback Results

Energy-Impact Differences The impact positions of lower energy particles spread out because of the field between the ESA exit and the detector at 2500 V eV hit positions w/2500 V on MCP keV hit positions w/2500 V on MCP

Simulation Results eV eV eV eV Energy Alpha-Elevation

Simulation Results 14 Beta-Azimuth Integrated Response

Tabulated Results Energy (eV) (eV/eV*rad) A(eff) (squ. cm)d(Beta) (rad)G(pixel)( squ cm*sr*eV/eV) e e e e e e e e-4 15 Geometric Factors are determined with Gosling’s formula: Where: A eff is determined by flying a normal incidence beam from a set area and then computing is determined by flying a normal incidence beam from a set area and then computing: And  is the coverage of one azimuth anode 22.5°= radians.

Ion: 21 V Elec: -21 VIon: -21 V Elec: 21 V Ion: 55 V Elec: -55 VIon: -55 V Elec: 55 V

17 Ion Def = 63 V; Electron Def = -63 V;

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Remaining analysis Scale simulation results to match calibration values – The simulation generally agrees with the calibration results with small differences – Example: Analyzer constant- simulated 10.6 vs calibration 10.8 Determine Geometric factor for each IES energy / angle step – Simulation values assume 100% grid transmission and 100% detector efficiency – Using 2003 calibration data, we can determine the scaling factor for 2 and 15 keV – Published MCP efficiencies will be used to fill in the remaining energies Produce an analytical model of the IES response