1. A Universal Atomic and Molecular
Detector for Atom Interferometry
Maxwell Gregoire
Cronin Lab
University of Arizona

2. Polarizability
E
d
p = Qd = α E
p: dipole moment Q: electron charge
d: displacement
E: electric field
valence electron cloud
nucleus

3. Diffraction
P

4. Mach-Zehnder Atom Interferometer
P

5. Mach-Zehnder Atom Interferometer
P
bars
block
transmission
P
bars
allow
transmission
P

6. Mach-Zehnder Atom Interferometer

7. Mach-Zehnder Atom Interferometer
-
+
● Creates phase shift in atom waves:
Φ proportional to α

8. The Problem: Current Detector
Langmuir-Taylor “hot wire” detector
● Thermal/surface ionization: atoms
contacting a filament ionize as they boil
off
● Efficient only if atom's ionization
potential is comparable to filament's
work function
atoms ions
Discriminator
&
Pulse
Counter
filament
CEM
ptable.com
ptable.com

9. The Solution: Universal Detector
● We want to be able to detect atoms from the entire
periodic table
● We want to be able to detect molecules
ptable.com

10. Motivations: Test Atomic Theory
● Test atomic theory:
polarizability, van der Waals coeff's, state lifetime,
branching ratio, and index of refraction calculations
all rely on knowing the
atomic dipole transition matrix elements
● Measuring one of those things tests the theory
ptable.com

11. Motivations: Parity Non-Conservation
● PNC research tests for beyond-the-standard-model
physics
● Observing the rate of parity-violating transitions
requires knowing the atomic dipole transition matrix
elements
ptable.com

12. Motivations: Atomic Clocks
● Atomic clocks use trapped atoms to keep time
● Limitation on accuracy is due to lack of knowledge
of blackbody radiation shift, which depends on
polarizability
ptable.com

13. Electron Impact Ionization Detector
Ionization
Regionatoms ions
Mass
Filter filtered
ions
Discriminator
&
Pulse
Counter
CEM

14. Electron Impact Ionization Detector
Ionization
Regionatoms
Mass
Filter filtered
ions
Discriminator
&
Pulse
Counter
SRS RGA 200 contains
● Quadrupole Mass Analyzer
● Channel Electron Multiplier
CEM
Build our own Discriminator
● AMPTEK A111, variable level
Use LabJack as pulse counter
ions
http://www.thomasnet.com/articles/instruments-controls/analyzers-residual-gas

15. Electron Impact Ionization Detector
Ionization
Regionatoms
Mass
Filter filtered
ions
Discriminator
&
Pulse
Counter
Design considerations:
● Ionization cross section
● Phase-space density
● Phase-space density limit/
beam divergence
● Filament heat/resulting noise
CEM
ions
Farland, Kinney, Phys. Rev. 137, A1058 (1964)

16. Electron Impact Ionization Detector
Ionization
Regionatoms
Mass
Filter filtered
ions
Discriminator
&
Pulse
Counter
CEM
atom beam being ionized
electron beam
Ideas:
● 1) shaped beam ● 2) almost-tangential beam(s)
ions

17. Electron Impact Ionization Detector
Ionization
Regionatoms
Mass
Filter filtered
ions
Discriminator
&
Pulse
Counter
CEM
Ideas:
● 3) pinching magnet along
with beam or filament source
ions
DeKieviet et al, Rev. Sci. Instrum. 71, 2015 (2000)

18. Acknowledgements
People
● Professor Alex Cronin
● PhD students: Will Holmgren (~2013) Ivan Hromada (~2014)
Raisa Trubko (~2015), Me (~2016), You (?)
● Undergraduates: Adam deBolt (2013), James Greenberg (2014)
Organizations
● University of Arizona Dept. of Physics
● National Science Foundation
● National Institute of Standards and Technology
Questions?