Fountain Spectrometer

Alexander KoukrasGyula NagyMiguel Fernández

Topics

• Geometry• Calibration• Transmission• Focusing properties• Resolution• Conclusions

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

Transmission (3 plates)

Now: T = 92% f does not change3rd plate not to lose

resolution

• 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• Compare 45º with theory:

1 2

0

x xR

x

Simion Formula45° 1.8% 3%

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

All information

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fountainspectrometer.blogspot.com

Thanks to our advisors:–Manolis Benis– Pilar Garcés

And all other CPOTS teachers

Thanks for your attention