Archived - First neutrons from Slovakia!
Posted: Sun Oct 21, 2012 3:59 pm
Hello, I'm a high school student from Slovakia and I already gave a
short description of fusor in my earlier post. Since then, with my
supervisor from Comenius University, we made new HV feedthrough which
resulted in much better stability of the discharge. Although we are
limited by voltage to 20 kV by our power supply, we managed to achieve
fusion and get some neutrons.
Our vacuum chamber is made from standard components. We use standard connectors and seals with aluminium ring which cause some problems with X-rays because aluminium is not good material for blocking X-rays. We managed to solve these problems by adding extra shield fromlead glass.
We´ve been using rotary and turbomolecular pump for achieving high vacuum. With this
apparatus we managed to achieve minimal pressure of about 2.10-3 Pa. Pressure was measured by the Thermocouple and the Penning vacuum gauge.
For preparing deuterium gas we used electrolysis of heavy water. Heavy water was electrolyzed by Polymer Electrolyte Membrane electrolyzer. This electrolyser causes some probles because water from oxygen side passed to hydrogen side. This problem was solved by adding a bubler for cathing water on hydrogen side. For purifing deuterium gas we used zeolite dryer, and between this dryer and electrolyser we put bubler with diffusion pump oil to prevent drying of electrolyser. Rate of deuterium production was kept higher than its consumption by fusor. Excess deuterium was released to atmosphere through another bubler with oil. Slow constant purging of the system was used also in order to improve
purity of deuterium gas. Then we put this deuterium into recipient by using precise leak valve.
The most problematic part was high voltage feedthrough and central electrode. Feedthrough was made from alumina tube with outer diameter of 10 mm and stainless steel rod. Smaller diameter of alumina caused sparking which was interfering with the neutron detector. Another essential thing was purity of central electrode. The electrode was first made from molybdenum, and later from tungsten. Both metals were cleaned by an electrolyte where they acted as anodes. For cleaning of molybdenum we used chromo-sulphuric acid. This acid is highly toxic and dangerous which was one of the reasons why we changed to tungsten. Tungsten was cleaned in 13% solution of sodium hydroxide. In both cases, stainless steel cathode was used during the cleaning process.
As a neutron detector, we used LiI crystal mounted on VA-S-50 Universal
scintilation probe. The whole setup was build by RFT company, East
Germany. As a moderator, we use polyethylene sphere with diameter of 10
cm. We measured background of 60 to 70 cpm because of high noise of
detector. With moderator and fusor running we measured about 80 to 100
cpm. Reference measurements with running fusor and without moderator
didn't show increased intensity of counts. The measurements were up to
2000 seconds long. In the figure, black errorbars show deviation
of 3 sigma, red ones shows 5 sigma. Sigma (standard deviation) was
calculated as square root of counts detected.
Do you find this to be reliable proof of fusion for “neutron club” membership?
Best wishes,
Michal Racko, under supervision of Michal Stano, PhD
short description of fusor in my earlier post. Since then, with my
supervisor from Comenius University, we made new HV feedthrough which
resulted in much better stability of the discharge. Although we are
limited by voltage to 20 kV by our power supply, we managed to achieve
fusion and get some neutrons.
Our vacuum chamber is made from standard components. We use standard connectors and seals with aluminium ring which cause some problems with X-rays because aluminium is not good material for blocking X-rays. We managed to solve these problems by adding extra shield fromlead glass.
We´ve been using rotary and turbomolecular pump for achieving high vacuum. With this
apparatus we managed to achieve minimal pressure of about 2.10-3 Pa. Pressure was measured by the Thermocouple and the Penning vacuum gauge.
For preparing deuterium gas we used electrolysis of heavy water. Heavy water was electrolyzed by Polymer Electrolyte Membrane electrolyzer. This electrolyser causes some probles because water from oxygen side passed to hydrogen side. This problem was solved by adding a bubler for cathing water on hydrogen side. For purifing deuterium gas we used zeolite dryer, and between this dryer and electrolyser we put bubler with diffusion pump oil to prevent drying of electrolyser. Rate of deuterium production was kept higher than its consumption by fusor. Excess deuterium was released to atmosphere through another bubler with oil. Slow constant purging of the system was used also in order to improve
purity of deuterium gas. Then we put this deuterium into recipient by using precise leak valve.
The most problematic part was high voltage feedthrough and central electrode. Feedthrough was made from alumina tube with outer diameter of 10 mm and stainless steel rod. Smaller diameter of alumina caused sparking which was interfering with the neutron detector. Another essential thing was purity of central electrode. The electrode was first made from molybdenum, and later from tungsten. Both metals were cleaned by an electrolyte where they acted as anodes. For cleaning of molybdenum we used chromo-sulphuric acid. This acid is highly toxic and dangerous which was one of the reasons why we changed to tungsten. Tungsten was cleaned in 13% solution of sodium hydroxide. In both cases, stainless steel cathode was used during the cleaning process.
As a neutron detector, we used LiI crystal mounted on VA-S-50 Universal
scintilation probe. The whole setup was build by RFT company, East
Germany. As a moderator, we use polyethylene sphere with diameter of 10
cm. We measured background of 60 to 70 cpm because of high noise of
detector. With moderator and fusor running we measured about 80 to 100
cpm. Reference measurements with running fusor and without moderator
didn't show increased intensity of counts. The measurements were up to
2000 seconds long. In the figure, black errorbars show deviation
of 3 sigma, red ones shows 5 sigma. Sigma (standard deviation) was
calculated as square root of counts detected.
Do you find this to be reliable proof of fusion for “neutron club” membership?
Best wishes,
Michal Racko, under supervision of Michal Stano, PhD