1. One way to improve first class mass measurements @ ISOLTRAP
Poilvert Nicolas, student session 2005

2. How do we measure masses?
THE basic idea: B +
Use a B field
→ radial confinement
Cyclotron frequency ωc= qB/m
q,m
Problem: motion not axially bound
2) super impose an E field
→ axial confinement
Poilvert Nicolas, student session 2005

3. The motion of the ion(s)
Three independent harmonic eigenmotions
1. Axial motion:
2. Magnetron motion (slow):
3. Reduced Cyclotron motion (fast):
Reduced
Cyclotron
A=100 amu, q=1, B=6 T
f+  1 MHz
f-  1 kHz
fz  44 kHz
Poilvert Nicolas, student session 2005

4. Beam coming from Isolde
Poilvert Nicolas, student session 2005

5. The experimental apparatus
Precision Penning Trap
MCP / Channeltron Detector
Penning Trap :
measure
Cyclotron frequency determination
Penning Trap :
cooling
Isobaric cleaning
2.7 keV ions
ISOLDE
60 keV ions
Paul Trap : RFQ-Buncher
Beam preparation
Poilvert Nicolas, student session 2005

6. But how exactly do you measure the mass?
Quadrupole exitation at ωrf : exact conversion between cyclotron motion and magnetron motion at resonance
G.Bollen et al.
resonant at ωrf = ωc
Courtesy of C. Yazidjian
Poilvert Nicolas, student session 2005

7. But how exactly do you measure the mass?
MCP / Channeltron
TOF
Precision Penning trap
B=5.9T
Poilvert Nicolas, student session 2005

8. How to determine B precisely?
a very high precision on m depends directly on a high precision of the B field magnitude
The solution is to measure B precisely using reference masses (alkali, carbon clusters,…)
Overall accuracy:
Poilvert Nicolas, student session 2005

9. The carbon cluster solution
Why Carbon clusters?
Pulsed YAG laser
λ = 532 nm
C13+
Gives us mass references throughout the nuclear chart
C5+
(12C)60 with 12C isotope
C22+
Poilvert Nicolas, student session 2005

10. Nuclear chart C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16
More reference mass
Reference mass

11. Precision Penning trap Carbon cluster ion source
My job
MCP / Channeltron
TOF detector
Find the right potentials in order to guide and inject the carbon cluster ions into the preparation trap
Precision Penning trap
RFQ cooler buncher
2.7 keV
ion bunches
ISOLDE beam
60 keV
Carbon cluster ion source
Laser
Poilvert Nicolas, student session 2005

12. Thanks for your attention!
Not to forget:
the ISOLDE group
and the ISOLTRAP collaboration
Special thanks to my supervisors
Poilvert Nicolas, student session 2005