characterizing the ebis-c spectrometer
DESCRIPTION
Characterizing the EBIS-C Spectrometer. Leah VanNahmen REU 2006 Kansas State University. Introduction. Spectrometer Basics Recoil Ions Beam Fragments Summary Applications. Spectrometer Basics. GOAL: Determine initial momentum of all products from a collision Gas Jet = Recoil Ions - PowerPoint PPT PresentationTRANSCRIPT
Characterizing the EBIS-C Spectrometer
Leah VanNahmenREU 2006
Kansas State University
Introduction
Spectrometer BasicsRecoil IonsBeam FragmentsSummaryApplications
Spectrometer Basics
EBIS-C Sp ec trom ete r
inte ra c tionre g ion
x-d irec tiony-d
irec
tion
De
tec
tor
Pa rtic le Bea m
GOAL: Determine initial momentum of all products from a collision
Gas Jet = Recoil Ions Particle Beam = Beam Fragments Detector MCP and PSD collect TOF and Final Position
Recoil Ions
We find recoil ions’ initial momentum from TOF using momentum conversion
Problem: Particles with different initial momenta can have the same TOF -50
13.98
14.04
14.10
different intial momentumand position can result in the same TOF
Comparison of Two Recoil Ions with Different Initial X Positions
TO
F (
use
c)
Momentum parallel to spectrometer (a.u.)
xi = 57.5 mm
xi = 57.4 mm
Recoil Ions
Make “voltage hill”
Best focusing if 2nd applied voltage is 82.8% of 1st voltage
Solution: Space and Time Focusing
5 10 15 20 25 30
0
200
400
600
800
1000
Voltage Decrease of Focusing Spectrometer (typical pattern)
Vo
ltag
e o
n P
late
(V
)
Plate Number
Recoil Ions
The EBIS-C spectrometer has great focusing!
82.0 82.5 83.0 83.5 84.0
-0.020.000.020.040.060.080.100.120.140.160.180.200.220.240.260.280.300.320.34
Best Space Focusing: 82.82%
Percent of Vs on 11th Plate vs. Error in Space Focusing
Err
or
(mm
)
Vf as a percent of V
s
82.5 82.6 82.7 82.8 82.9 83.0 83.1
20
40
60
80
100
120
140
160
Best Time Focusing: 82.75%
Percent of Vs on 11th Plate vs. Error in Time Focusing
Err
or
(pic
ose
con
ds)
Vf as a percent of V
s (Volts)
Beam Fragments
Magnification of Y Position
Magnification of Y Velocity
Problem: Magnification
Spectrometer AxisSpectrometer Axis
D = vt
Beam Fragments
0 1 2 3 4 5
1.06
1.08
1.10
1.12
1.14
1.16
1.18
1.20
1.22
1.24
1.26
1.28Data: EsclvsMagYPos_MyoModel: Upside-down Morse Potential Chi^2/DoF = 1.7187E-6R^2 = 0.99972 P1 0.12996 ±0.00359P2 2.34253 ±0.04856P3 0.39072 ±0.0099P4 1.0552 ±0.00847P5 0.29636 ±0.01993
Magnification of Y Position as a Function of E
scl
Mag
nif
icat
ion
of
Y P
osi
tio
n
Escl
Solution: Find an equation to correct for both kinds of magnification
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.51.021.031.041.051.061.071.081.091.101.111.121.131.141.151.161.171.181.191.201.21
Data: EsclvsMagVelo_MvelocityModel: ExpDec2 Chi^2/DoF = 7.3441E-7R^2 = 0.99989 y0 0.99362 ±0.08449A1 0.0908 ±0.052t1 6.23221 ±11.61012A2 0.14413 ±0.03213t2 0.81316 ±0.13532
Magnification of Y Velocity as a Function of E
scl
Mag
nif
icat
ion
of
Y V
elo
city
Escl
Beam Fragments
Overall Magnification Solution:Overall magnified Y position =
magnification of Y position x initial y position + magnification of Y velocity x initial Y velocity x TOF
Ym = MYi x Yi + MVy x vy x TOF
Summary
Apply two voltages to spectrometer to focus recoil ions
Correct for magnification of beam fragments
End up with enough equations to find the initial momentum of all the products from a collision
Applications
This characterization will allow experimenters to quickly and easily focus the EBIS-C spectrometer and correct for the magnification it causes
The spectrometer will be used in the EBIS-C beamline for future experiments…..
Applications
Gas JetParticle Beam
Physics
CO Ar11+ Dissociation of CO2+
Ar/He HD+ and H2+ CID and DC
He H2+ Vibrational State
Effects
Applications
In Ar/He experiment:
Ar + H2+
H+ + H + ArH + H + Ar+
De
tec
tor
Sp ec trom ete r a xis