The project officially ends.
21.03.2011. - 25.03.2011.
I. Živković and I. Levatić visited Lausanne. With J. Piatek worked on the implementation of the pickup coil inside the dilution refrigerator.
Testing the piezo-motor inside the He3 system (the picture is rotated 90 deg counter-clockwise).
Piezo-motor is mounted on triangles made out of delrin. On one side there is a fiberglass tube which has CuBe springs at the bottom. On the other side is a loosely connected attachment to the He3 pot. When placed inside the IVC (inner vacuum chamber) can, Cu-braided strips mounted on the back of the piezo-motor allow for a good thermal contact to the He4 bath thus removing all the heat generated when the piezo moves. In this arrangement we have managed to fully move the piezo-motor (20 mm) in a reasonable time (10-20 min). The temperature of the He3 pot has been stable at 275 mK with minor changes of a couple of milliKelvin. This design can still be improved to achieve faster travel.
There are also two black sticks (carbon-fiber) on this picture. One is firmly tightened to the moving part of the piezo-motor while the other one is positioned co-axially with a fiber-glass tube (where the pick-up coils will be placed) and will serve as a sample holder. They are joined together with a small delrin piece. This is to reduce the heat flow from the piezo-motor towards the sample.
Presentation of the work and the results of the project on the conference held at the Institute of Physics.
01.02.2011. - 08.01.2011.
I. Živković visited Lausanne. With J. Piatek successfully installed new coaxial cables and got the squid working inside the dilution refrigerator.
19.01.2011. - 21.01.2011.
Testing the squid inside the He3 system using new coaxial cables.
The piezo-motor, payed by the prof. Ronnow's laboratory, finally arrived in Zagreb, after more than 4 months of bureaucracy.
Semi-rigid coaxial cables arrived from USA.
26.08.2010. - 31.08.2010.
Ivana Levatić and Ivica Živković visited Lausanne. Together with Julian Piatek we were able to put together the holder for the piezo-motor, alongside the pick-up coils for the squid.
On the above picture one can see the piezo-motor attached to the copper block which is directly in contact with a mixing chamber. On the other side there is a delrin piece (strong plastic which can be used for low temperature frames) with a hole where the carbon fiber rod goes through. Towards the bottom of the rod there is a small sample attached to it.
Later on we have attached the carbon fiber tube which had a pick-up coil on it (made out of the superconducting NbTi wire). Also, on the bottom of the tube, one can see the CuBe springs which were used to center the tube inside the IVC (inner vaccum chamber) of the dilution fridge. They also serve to prevent the movement of the pick-up coils inside the magnetic field.
Inserting the system in IVC was effortless. The minimum temperature read at the mixing chamber was 55mK. That should be compared to the last cool-down of the fridge without the piezo assembly when the minimum temperature was 33mK. That means that the thermal link from the walls of IVC, over the CuBe springs and further up towards the mixing chamber is truly minimal. We can say that our approach has passed the test.
A visit form dr. Michael Mueck, the manufacturer of the SQUIDs. Finally managed to get the SQUID working. Why it wasn't working before? The major problem is the presence of a very strong RFI (radio-frequency interference), most probably coming form the TV tower located at the nearby hill. A special attention has to be payed to the proper shielding and grounding.
Prof. Henrik Ronnow visited Zagreb.
24.03.2010. - 27.03.2010.
Not able to make the SQUIDs work, visited the manufacturer in Germany.
SQUIDs arrived in Zagreb.
Piezo arrived in Lausanne. Room temperature testing done, it works.
Discussed with prof. Basletić, in-charge of the He3 system, on how to use it and what modifications can be done.
The first equipment for the project has been ordered: the SQUID sensor with electronics from
and piezo-based linear positioner from
. Initially, SQUID will be tested in Zagreb while the positioner will be tested in Lausanne in the laboratory of prof. Henrik Ronnow. Later on, we will combine those two to achieve the linear motion of the sample through the pick-up coils and obtain the absolute value of the magnetization
The project has officially started. The contract has been signed by dr.sc. Ivica Živković
the Institute of Physics
, Zagreb (represented by dr.sc. Petar Pervan) and
the Ministry of Science, Education and Sports
(represented by prof.dr.sc. Dražen Vikić-Topić).