Transcript CERN workshop 2015

Dag Hanstorp
Photo detachment of negative ions at ISOLDE:
Towards measuring the Electron Affinities of Radioactive Elements
S. Rothe, B. Marsh, R.E. Rossel, V. Fedosseev, M. Veinhard , T. Kron,
D. Hanstorp, J. Welander, K. Wendt A. Ringvall-Moberg, Y. Liu,
T. Day Goodacre, R. Heinke and J. Sundberg
ISOLDE workshop and users meeting 2-4 December 2015
Long range forces in atomic systems
Coulomb force ~ 1
r
Polarisation ~
Penetration ~
1
r4
1
er
Properties of Negative Ions
• Small Electron affinities (EA)
(appr. 1 eV)
Energy
• Few (if any) excited states
• Optically allowed transitions
only observed in Os- , Ce- and La• La- is a good candidate for laser cooling
EA
 sympathetic cooling of antiprotons
X-
X
Why is the sun yellow?
Blackbody radiation
At T = 5780 K
Fusion reactions require
T = 100 MK
Energy
Ivanov VK
RADIATION PHYSICS AND CHEMISTRY
70 (1-3): 345-370 MAY-JUN 2004
0,75 eV
H-
H
(Wildt, R. APJ, (1941), 93, 502 )
Targeted Alpha Therapy (TAT)
cancer cells
a - range
Target
Carrier
Receptor
Antibody
Immunology
Structural biology
211At
particularly suitable isotope
• 7 h lifetime
• No long lived daughters
• Non-toxic daughters
• Suitable a energy
Coordination
chemistry
Linker
Radioactive
payload
Nuclear physics and
radiochemistry
Astatine
•
Least abundant element on earth
•
70 mg in the crust of the earth (1 atom per 100 kg mass)
•
Small knowledge about chemical and physical properties
•
Behaves sometimes like a metalloid sometimes like halogen - a chemical hybrid
Motivation for EA measurement of At and Po
Astatine
• EA equally important as the IP
 determine electronegativity
 nature of chemical bonds
• Important for computer simulations
for binding of At to receptor
• No experimental value for EA(At) yet
PHYSICAL REVIEW A 91, 020501(R) (2015)
• Scattering of theoretical predictions ~1 eV
• Po is considered important component of the
natural radiation affecting humans
• Physico-chemical properties need to be understood
to develop decorporation treatments
electron Affinity (eV)
Pollonium
F
Cl
Br
I
3
PHYSICAL REVIEW A 91, 020501(R) (2015)
At
S
2
expt.
4c+CCSD(T)+breit+QED
MCDF+empirical
DK6+DFT
O
Se Te
Po
117
Lv
1
20 40 60 80 100 120
Atomic number
Letter of Intent (LOI) INTC-I-148
https://cds.cern.ch/record/1603086/files/INTC-I-148.pdf
Collinear photodetachment spectroscopy
P- + hn  P + eEnergy
3P
0
3P
1
3P
2
Wigner law:
s= k (E-E0) l+1/2
P-
P
GANDALPH
Gothenburg ANion Detector for Affinity measurements by Laser PHotodetachment
I-
ITO covered glass
e-
For each laserpuls:
Signal:
0.01 atom
Background:
1014 photons
Drawing:
Annie
Ringvall
-Moberg
GANDALPH
Built in the spring 2015 at University of Gothenburg using existing equipment
Moved to ISOLDE, June 2015
Installed an put into operation at GLM
full control of system
Laser transport from RILIS
Run HRS in positive mode in parallel
Photodetachment of I-, July 2015
RESULTS: Photodetachment of I460 pA of 127I measured on GPS FC.490
28pA
Low 10-8 mbar vacuum through
~ 8% transmission to the neutral detector
Photodetachment signal of IThreshold still measurable at very low ion rates
(<1 pA, FC noise)
< 1pA
Everyone has been young
I was young in 1985
Göran Andersson (one of the founders of ISOLDE) retired
and was succeeded by Björn Jonson
Björn gave me the isotope separator LILLJON
 I could start investigating negative ions
Summary
GANDALPH shown to work
Full proposal will be submitted 2016
Looking forward to future ISOLDE user meetings
when the EA of At- and Po- will be presented!
Thanks to staff at ISOLDE for support!
Thank you for your attention!