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Twisted Electrons Planning Discussion

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Presentation on theme: "Twisted Electrons Planning Discussion"— Presentation transcript:

1 Twisted Electrons Planning Discussion
April 1, 2015 Joe Grames

2 Step 2 – Evaluate path forward Step 3 – JLAB Tests
Goals A big success to demonstrate modified Mott cross-section Even more success learning how making twisted electrons from GaAs Ground-breaking success demonstrating spin-polarized twisted-electrons Exceeding success if demonstrated with a GaAs-tip Step 1 – U. of Oregon Tests Learn if/how Ben’s electron gun can accept Mott style detector Test Dipangkar’s modified Mott cross-section w/ and w/o twisted electrons Step 2 – Evaluate path forward Step 3 – JLAB Tests Test if GaAs makes twisted electrons using holographic filter + imaging If GaAs unsuccessful consider adding FE-source Learn how to fabricate and operate (HV or light) Characterize beam brightness vs. GaAs (how different?) What are the limitations Test Dipangkar’s modified cross-section w/ and w/o twisted electrons

3 100 keV Mott Scattering Chamber
Port Angle Solid Angle (sr) Forward ±50° 5.1 x 10-5 Backward ±120° 5.5 x 10-4

4 Maximum Analyzing Power vs. Kinetic Energy
Polarized cross-section : Unpolarized cross-section :

5 1990’s Setup and Result T = 100keV, q = 120° Most equipment available
CF mount surface barrier detector Mini NIM crate Bias supply Pre-amp to improve S/N Amplifier Pulse height analyzer/ADC Inelastic Elastic R ~ 1 Hz/(nA-Å) Typical I = 1–10 nA T = Å

6 Photo-Emission and? Field-Emission
Use HV to achieve FE Use anode for control? Photo-assisted FE? V=100kV

7 Oversimplified Test Stand Idea ?
HV < 200 kV Polarized Laser Polarized photoemission Photo-assisted FE??? Mott Polarimeter Entrance aperture Scattering 50, 120 deg Asymmetry measurement Current monitoring Mount to standard moly puck GaAs photocathode FE emission tip Intensity Control Slit/aperture Cup/Plate monitor Twisted Generator Cross Grating YAG viewscreen/camera

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