Alexander Koukras Gyula Nagy Miguel Fernández. Topics Geometry Calibration Transmission Focusing...
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Transcript of Alexander Koukras Gyula Nagy Miguel Fernández. Topics Geometry Calibration Transmission Focusing...
Geometry• Just PPA with 2π cylindrical symmetry (rotating
around x axis)• Advantage compared to PPA:– Greater acceptance: more solid angle (2π symmetry)
Calibration
•
• Linear relation between E0 and Vd
• Here, q=-1 (e) so
• For 45º
0 dE q f V
0xf2d
0 dE f V
Relation Vd, E0 :Using LUA
Slope
Formula
Calibration (45º & 30º)
-1200 -1000 -800 -600 -400 -200 00
100
200
300
400
500
600
700f(x) = − 0.572916209368053 x + 0.139941427115787R² = 0.999479768967151
KE vs V 45º
Vd (V)
KE (e
v)
f 0.573
0x 103f 0.576
2d 2 90
-1000 -900 -800 -700 -600 -500 -400 -3000
100
200
300
400
500
600
700
f(x) = − 0.663829432665721 x + 0.205908414420321R² = 0.99982220796473
KE vs V 30º
Vd (V)
KE (
eV)
f 0.664Slope
Transmission
• T(%) =
For a fixed KE of particles and its corresponding Vd (calibration)
Fly particles slightly different angles measure #particles enter, #particles pass through
• 45º T= 98.5%• 30º T= 20% !!!• Wider exit slit + 3rd plate (only for 30º)
# particles pass through100
# particles enter
• For 45º 1st order focusing, focus inside• For 30º 2nd order focusing, focus outside
Trace width:
Focusing properties
Simion Theoretical
30º 0.2 0.03
45º 2 1.3
20x 2x
Resolution
• Lua program to scan energy, measure the Emin and Emax that leave the exit slit, and calculate RThe lower R the better
max min
0
E ER
E
max min
0
E EE
2
R 45 º 1.8 %30 º 1%
Resolution
• Independent of energy
• 30º has better resolution for same geometry
• For 30º, R does not change with 3rd plate + wider exit slit
Conclusions
• Better resolution for 30º
• Better focusing for 30º
• Lower transmission for 30º – Solution: 3rd electrode + wider exit slit