1. Preparing antihydrogen at rest for the free fall in
Laurent Hilico
Jean-Philippe Karr
Albane Douillet
Vu Tran
Julien Trapateau
Ferdinand Schmidt Kaler
Jochen Walz
Sebastian Wolf
2014 – 2017
Bescool project
WAG November 2013 Bern

2. Outline H+ motion control requirements Capture and cooling challenges
Experimental progress

3. GBAR overview

4. by laser cooled Be+ ions
Last GBAR steps H
H+ Capture
and cooling
by laser cooled Be+ ions
Threshold
Photodetachment
l=1.7 µm
Reaction
chamber
H at rest
Recoil 0.23 m/s g H+
keV
Temperature eV e+
30 cm
Accurate measurment of g < 1 % H
initial velocity Dv0 < 0.8 m/s H+
3 neV, 20 µK

5. H with v0 < 1 m/s ? Cooling challenges
Ground state quantum harmonic oscillator
m = kg , Dv0 < 0.8 m/s
w < 3 MHz
Cooling challenges
Reaction
chamber
Cold trapped H+
Capture + Cooling
Kinetic energy keV
Temperature eV K
Trapped particule
Temperature neV
20 µK ÷
Frontiers of
Quantum world
NIST D. Wineland
Innsbruck R. Blatt
Classical world

6. > 10 000 laser cooled Be+ ions
Two Cooling Steps
First step
Capture and sympathetic Doppler cooling by laser cooled Be+ ions
in the linear capture trap (Paul trap, r0 = 3.5 mm, W = 13 MHz) H+
few mm
313 nm laser
300 eV, T = K T
÷ 3 109
> laser cooled Be+ ions
100 neV, T ~ mK
Second step
Transfer and ground state cooling
of a Be+/H+ ion pair in the precision trap
F. Schmidt Kaler, S. Wolf , Mainz

7. Capture efficiency First step t time Versus intake delay
Be+ laser cooled ions
1 keV H+ ions
time
Ubiais=980 V
H+ intake
0 V t
Biased linear RF Paul trap
Output end-caps
Input end-caps
1000… 0 V
Versus intake delay
Versus initial temperature (eV) t eV

8. Sympathetic cooling time
First step
Numerical simulation 500 Be+ and 20 H+ v
t = 0 s
Ec= 2 meV
313 nm laser
t = 8 ms
Hotter H+ ions and larger ion clouds numerical challenge
Work plan : Experimental tests with matter ions H2+ or H+

9. Precision trap – motional couplings
Second step
Precision trap – motional couplings
Two coupled oscillators in an external potential
x,y z
z trapping DC potentials
x,y trapping RF effective potentials
Coulomb interaction coupling H+
Be+
Newton equations equilibrium positions small oscillations
in phase mode
out of phase mode
normal modes
individual ion modes
x, y, z
T. Hasegawa, Phys. Rev. A 83, (2011)
J. B. Wübbena, S. Amairi, O. Mandel, P.O. Schmidt, Phys. Rev. A 85, (2012) 1D 3D

10. Precision trap – motional couplings
Second step
mlc/msc
b12
z motion
x,y motion
Efficient
sympathetic cooling
mLC/mSC  b1 = 50 % b2 = 50 %
mLC/mSC = 9/1 b1 = % b2 = % ?

11. Doppler cooling in precision trap
>> 20 µK

12. Raman side band cooling
w0-D+dhfs- wi
w0-D
Stimulated Raman transition
Spontaneous Raman transitions H+
Be+ w0
D ~ tens of GHz
2P3/2
F=0, 1, 2, 3
3 laser freq.
2 beams
2P1/2
F=1, 2 nm
2S1/2
n=2
dhfs= 1.25 GHz
n=3
n=2
wvibr

13. Raman side band cooling
Second step
Stimulated Raman transition no spontaneous emission coherent process
Rabi oscillation D
Population transfert probability
Lamb Dicke parameter
For n → n-1,
p pulse duration
n=2
Single ion
b1 = 1
3 modes
t ~ 100 µs /n/mode
Be+/H+
b1z = 0.18
2 modes
x 5
b1x,y =
4 modes
x 15
~ 10 ms
< 1s
n=3
n=2

14. Experimental progress

15. Capture trap design Jean-Philippe Karr Hot H+
RF V at 13.3 MHz, r0 = 3.5 mm
DC’s V
313 nm cooling laser
Quadrupole
guide
12 mm RF DC
O V DC

16. Transfer to precision trap
Design: Sebastian Wolf, Mainz
Capture trap
Photodetachment
l = 1.64 µm
~2 mm
Cooling
l = 313 nm
Mainz implantation trap

17. Vacuum vessel
with cryopumping H+
Capture trap
Precision trap

18. Work plan 2013 2014 2015 2016 Evaluate sympathetic cooling times
11/2013
12/2013
2013
Achieve the design
Setup the cooling lasers
03/2014
12/2014
2014
Capture trap implementation
Test with H2+ and H+ matter ions
from the REMPI source
Precision trap implementation
Test with Be+ and Ca+ ions
06/2015
12/2015
2015
Evaluate sympathetic cooling times
numerically & experimentally
Transfer of precision trap
to Paris,
03/2016
12/2016
2016
Be+ and H2+ transfered
in precision trap
Be+/H2+ ground state cooling

19. Tests with a H2+ / H+ REMPI source
303 nm pulsed laser
3-4 mJ H2
H2+ ions
Ec = 50 eV
dE ~ 10 meV
100 %
efficiency
H2+ ions
Ec = 0 eV
dE ~ 200 meV
P=10-6 mb
Ion creation
P=10-8 mb
Ion optics
P=10-10 mb
Injection into the quadrupole guide
H+ Gbar
H2+ metrology project
HCI highly charged ions 40Ar13+, P. Indelicato, C. Szabo
Synergies

20. PhD positions available
Conclusion
Capture of > 10 eV H+ and Doppler cooling in a linear Paul trap
Transfer to precision trap
Doppler and ground state cooling in precision trap OK OK
PhD positions available
ANR BESCOOL
ITN ComiQ

22. Double well structure with
Can we improve the motional couplings ?
Idea
wcoul
Efficient coupling w1 w2
Trapped ions w1 ~ w2 ~ MHz wCoul ~ 100 kHz
Coulomb coupling
z12eq < 40 µm
z12eq
Single well
with m1 = 9, m2 =1
wz 2 ~ 3 wz 1
poor couplings
wx 2 ~ 9 wx 1
Double well structure with
very small electrodes ?
Possible solution