The User-friendly On-line Diffusion Chamber

Jaime E. Avilés Acosta

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

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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

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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

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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

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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

Questions?

Spectrum Master

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