Outline
1) What experiment did I work on?
2) What is the experiment’s goal?
3) What was my project?
4) What was done and what is yet to be done?
5) Future prospects for the On-line Diffusion Chamber
The Experiment
On-line Diffusion Chamber (ODC) built in 2009 by
team from Universität des Saarlandes
The ODC is a stand-alone apparatus for
radiotracer diffusion studies
Uses a radioactive isotope beam source to
implant radioactive impurities in a target
material
Spectrum Master
X-Cooler II
Implantation
Target placed in chamber, held by
a manipulator arm
Chamber is plugged into beamline
System pumped down
to vacuum mbar)
Radioactive isotopes are
beamed into the target
The Experiment
So, how does it work…?
Spectrum Master
X-Cooler II
Annealing
Manipulator arm extends target to oven
Target annealed to diffuse implanted
radioisotopes
After annealing,
target is drawn back
to chamber
The Experiment
Spectrum Master
X-Cooler II
Ablation
Argon gas is ionized and then
accelerated with a 60 kV potential
Ion gun ablates target’s surface
Ejected material and
implanted radioisotopes
cling to tape
X-Cooler II
Tape transport and diffusion profiling
Tape moves over gamma detector
that operates at ~80 K
Detector records intensity
of radiation over time
Data are used to build a
diffusion profile of the
radioisotope in target.
The Experiment
Spectrum Master
What’s so special about the ODC?
Direct access to on-demand production of
radionuclides at ISOLDE
The experiment is run almost only
with a LabView program—all data
is stored in the computer running it
The Goal
341
The purpose of the ODC is to carry out studies
with short-lived radioisotopes or nuclear isomers
(half-lives in tens of minutes)
However, the ODC was too unwieldy
and complicated for visiting
researchers to carry out experiments
in a short period of time.
My Project
Make the ODC more mobile and easier to plug-in/plug-out of beam line
Calibration of peripherals (ion gun, Ge detector, Faraday cup, etc.)
Improve execution timing of LabView code of Virtual Instrument that controls ODC peripherals
Test apparatus with stable beams and radioactive isotope beams—compare results to offline diffusion apparatus
Software Changes
Added annotations throughout the LabView block panel (the “code”)Wrote an in-depth guide to explain how it worksRemoved unnecessary flat-sequencestructures to enable parallel processing
Faraday Cup on the ODC couldn’textend fully due to a series of misused variables and booleans, now replaced
Software Changes
Most of the time, the program periodically scans for output from all the peripherals and stores the dataModified the code to add a timing functionality to see if changes in the code improved execution timingScanning time improved by an average of 71.8 ms (the scan takes ~2 seconds, it runs 24 functions, with 83 ms per function).
Numerous other miscellaneous changes—all changes have been logged for future reference
Hardware Changes
Assembled a new three-phase plug for the ODC’s controller rackAdded two pressure gauges and two needle gauge displaysAdded a turbo motor pump Added a halogen LED
inside the chamberInstalled heavy duty wheels
(no more forklift needed!)
Fara
day
Cu
p
Target Axis
Beam
Axi
s
Calibrated Faraday Cup pre-set positions and the target holder’s origin’s position (0 mm)Attached cooling fan to turbo motor pump
Hardware Issues
After cooling down, Ge gamma detector didn’t seem operationalTried to bias detector with multiple HV supplies with no luckWarmed and cooled down detector again over a 48 hour periodFeedback from Ortec DSPEC Jr signal processor suggested power failureUsed a HV supply with an ammeter—current wouldn’t drop despite increasing voltage The above suggests a short-circuit in detector
The Future of the ODC
Ge gamma detector will be sent to GSI for further diagnosis and for repairs
A draft of a complete user guide for the ODC will be compiled
Future students will finish calibrations, tests, and improvements (with the help of new documentation, of course)
The much more user-friendly ODC will allow future users to use it for studies with short-lived radioisotopes during their short stays at CERN
Acknowledgement
My adviser, Karl JohnstonTorben Molholt
Haraldur “Palle” GunnlaugssonJoão Guilherme
The rest of the staff at
The University of Michigan Indiana University Bloomington CERN