Project   KATRIN


The aim of the international project KATRIN (KArlsruhe TRItium Neutrino experiment) is to improve the sensitivity of determination of the electron neutrino rest mass by one order.

Neutrino was established by Swiss physicist Wolfgang Pauli in 1930. The reason to introduce it was as follows:

   During the beta-decay, an atomic nucleus with the atomic number Z changes to a nucleus with atomic number Z+1 and an electron which is emitted. The charge is conserved - the positive charge of the nucleus increased by one and one negative charge (electron) appeared to eliminate this increase. However: the continuous energy distribution of the electrons was confusing. According to the law of conservation of energy, the energy of the electron should have a sharp value equal to the difference of the mother and daughter nuclear masses. It turned out that it is not the case - the outgoing electron can have any energy between zero and the above difference. To rescue the law of the conservation of energy (which is the very basic law of the contemporaneous physics), Pauli suggested that during the beta-decay not only electron but also another electrically neutral particle - neutrino - is emitted. The total beta-decay energy is distributed between the electron and the neutrino and the energy conservation is O.K.

Naturally, it was a hypothesis only that time. It has to wait for verification until 1956 when the American physicists Reines and Cowan proved the neutrino existence experimentally. Immediatelly after finishing the experiment they sent a telegram to Pauli announcing the successful proof of the neutrino existence.

Anyway the question "Is the rest mass of the neutrino zero (as e.g. that of photon) or not?" was unsolved until very recently. It is, however, of crucial importance in the elementary particle physics as well as in the astrophysics and cosmology. The theoretical physics is unable to solve it; highly sensitive experiments are necessary. Such experiments are extremely difficult - at the edge of today's technological possibilities. The first indirect proof of non-zero neutrino mass was evidence for so called neutrino oscilations in the experiment Super-Kamiokande in 1998. (In short: there exist three species of neutrino - the electron, muon, and tauon ones. Under some circumstancies, they can spontaneously "change" one into the other - oscillate.) In 2002, an analogical effect was found in Sudbury Neutrino Observatory. In December 2002, the experiment KamLAND proved the existence of oscillations also for the antineutrinos. Now, the non-zero rest mass of neutrino is generally accepted. However, the question "How big (or, better, small) the mass is?" remains.

The method used in the project KATRIN is to measure the endpoint region of the energy spectrum of the tritium beta-decay. (Tritium is the heavy isotope of hydrogen with the mass number A=3.) If the neutrino has non-zero rest mass, the shape of the spectrum differs from the case of the zero rest mass. The differences, however, are exiguous and the demands on the sensitivity and accuracy of the experiment are therefore enormous.

The project KATRIN does not start 'on a green field'. In some sense it is a continuation of the passing experiments in Mainz (Germany) and Troitsk (Russian Federation). Both these experiments consist of measurement of the tritium beta spectrum using so called integral electron spectrometers. They are the instruments which combine high transmision and good resolution. This feature is indispensable for the measurement of detail shape of the beta-spectrum in the endpoint region.

Both the Mainz and Troitsk experiment proved that if the neutrino rest mass is non-zero, it is less than 2.2 eV (Mainz) and 2.5 eV (Troitsk). Further decrease of this limit is out of the possibilities of those experiments. The project KATRIN will construct an analogical spectrometer but of considerably larger dimensions. To have an impression: following the first proposal, the main spectrometer chamber was suggested to be a cylinder of 7 m diameter and more than 20 m length. (The Troitsk spectrometer has the diameter of about 1.3 m and length of 7 m, the Mainz one is yet a little smaller.) The preliminary calculations (see Letter of Intent) show that such a spectrometer is able to determine the upper limit of the neutrino mass at the level of ~0.3 eV. However, the international Review Panel which was created in 2002 to judge and evaluate the proposal of the experiment has suggested to increase the dimensions of the main spectrometer to about 10 m. This suggestion has been carefully discussed and thought over, and during the Collaboration Board meeting in December 2002 it was accepted. At the end of 2004, the Design Report, 250-pages basic document of the project has been issued.

The project is an international one. It was initiated by the physicists from Mainz and Troitsk, who utilize many-year experience in this field. Further, a great group of fellows from Forschungszentrum Karlsruhe (where the whole apparatus will be mounted) takes part. Finally - the last but not the least - people from other research facilities who can contribute to the solution of various problems were addressed. The constituent members of the collaboration are then the following facilities: Johannes Gutenberg Universitaet Mainz (Germany), Nuclear Research Institute Troitsk (Russian Federation), four different departments of Forschungszentrum Karlsruhe (Germany) [Institut fuer Kernphysik, Institut fuer Prozessdatenverarbeitung und Elektronik, Institut fuer Technische Physik, Tritium-Labor Karlsruhe], Fachhochschule Fulda (Germany), Universitaet Karlsruhe (Germany), Nuclear Physics Institute of the Czech Academy of Sciences (Czech Republic), University of Washington in Seattle (U.S.A.) and Friedrich-Wilhelms-Universitaet Bonn (Germany).

During the 3rd Collaboration Meeting (Mainz, Dec. 5-6, 2002), the Collaboration Board accepted the application of the physicists of the University of Wales at Swansea to participate in KATRIN. So the University of Wales became the next full scope member of the project. Moreover, the associate membership was offered to the JINR Dubna, Russia.

As the time glides, the KATRIN project attracts further and further people. During the 4th Collaboration Meeting held June 1-4, 2003, in our Institute in Rez, we welcomed the ASTEC group from Daresbury Laboratory (Great Britain) between us. In connection with the Professor Weinheimer's crossover to Westfaelische Wilhelm-Universitaet Muenster in 2004, this University also became a member of KATRIN (and in no case a negligible member). In 2007, also Massachusetts Institute of Technology joined the project.

At the beginning of 2003, there were published results of the cosmic probe WMAP (Wilkinson Microwave Anisotropy Probe), which - as we see from its name - studies the cosmic microwave radiation. These results when combined with results of other experiments indicate (see e.g. here), that the sum of the masses of all three neutrinos (electron, muon, and tauon ones) should be less than 1 eV. This means that the electron neutrino mass should be of order of maximally tenths of electronvolt. However, it is necessary to keep in mind that these results are not model-independent. On the contrary, they are based on assumption of validity of some cosmological models.

In the meanwhile, the works in the KATRIN project continued. Parts of the spectrometer are already under construction. Moreover, various calculations cotinue to take into account all effects which could ever so little affect the precision of the experiment's results. Based on the latest calculations, the Collaboration Board came (during the 4th Collaboration Meeting held June 1-4, 2003, in our Institute in Rez) to the conclusion that KATRIN is able to determine the upper limit of the electron neutrino mass at the level of 0.2 eV. This is analogical result as that of the WMAP one but will be achieved by different and, moreover, model-independent approach.

During 2003, the pre-spectrometer for KATRIN was built and now it is carefully tested. At the 5th Collaboration Meeting (Karlsruhe, Dec. 11-12, 2003), it was christened as "KATRINKA".

In June, 2004, there was next, the sixth, Collaboration Meeting. Now, it took place in Moscow, from 6 to 8 of June. Similarly as during all previous Meetings, there was a lot of contributions concerning the present status of the Project as well as the next assignments, both immediate and long term.

The seventh Collaboration Meeting took place in November 2004, in Karlsruhe again. The pre-spectrometer KATRINKA is now installed into a testing chamber and thorough tests continue. As for the remaining main parts of the whole instrument (the main spectrometer and the tritium source), the contracts with the producers were signed. The progress of the project proceeds as planned.

The up-to-now last, the eighth, Meeting was organized in Muenster in March 2005. The dealings were similar to those at the preceeding Meetings - progress of particular tasks, search for possible weak points and their elimination. Nevertheless it turned out that no serious problems appeared.

The Meetings take place regularly, more or less every half year. The next, ninth, Meeting was then organized in September 2005, this time in Karlsruhe again. As usually, the agency was very comprehensive. During three days, altogether 10 plenary contibutions and 41 ones in three parallel sessions were read. As always, they brought a summary of the Project present state, of the particular tasks already resolved, and - also - what is needed to do in nearest future. Except the readings, many informal discussions were hold during breaks and after the end of everyday official program.

The jubilee - the tenth - Meeting took place March 2006 at the Internationales Forum Burg Liebenzell, the place where the project was initiated. (The first meeting of the physicists who proposed the project went on just here, in January 2001.) The eleventh Meeting was organized in Karlsruhe again, in September 2006. Both these Meetings engaged mosty in routine agenda. The latter one, however, was strongly influenced by a piece of joyous news: the main spectrometer is within an inch of finishing, the leak and vacuum tests passed successfully.

The spectrometer chamber was manufactured in MAN-DWE Gmbh factory in Deggendorf. After completing it was necessary to transport it into FzK Karlsruhe. Deggendorf is only some 300 km as the crow flies from Karlsruhe. Nevertheless, road transportation of a steel cylinder of 10 m diameter, more than 20 m length, and about 200 metric tons of weight turned out to be impossible. The only possible way appeared to be a shipment even when the transport length had been a little longer - almost 9000 km. The route led along the Danube river to the Black Sea, then through the Mediterranean Sea, Strait of Gibraltar, along the Portuguese and Spain coast, through the Channel until the mouth of the Rhine river and, finally, on the Rhine to the Leopoldshafen near Karlsruhe (see map). The spectrometr was embarked on September 28 onto a riverboat. Then it was transfered successively onto two seaships. Due to low water in Rhine, the last part of the transport had to be done using a pontoon. On October 25, the spectrometer arrived to the port in Leopoldshafen. Then, the last 7 km of a road transport remained. This last part was in no case easy as it can be seen on this video. (Anyway, the waterborne traffic had not been easy, too. At one place, the uppermost part of the chamber went only 7 cm below a bridge.) Finally, the spectrometer was set into its place - into the building which had been specially built for it. (A more detailed description of the transport may be found here.) One important period of the project was thus completed.

During 2007, there were again two Collaboration Meetings (March and October), both in Karlsruhe. They were devoted to the routine agenda; all works run satisfactorily. The main spectrometer no longer resembles a giant pipe, it starts to look like a serviceable instrument.

On Oct. 1, 2009, the Forschungszentrum Karlsruhe merged with the University of Karlsruhe into one educational and research unit, the Karlsruhe Institute for Technology (KIT). This change had no consequences for the KATRIN project.

Until March, 2010, the Collaboration Meetings were organized regularly (twice per year) and the project runs at its usual pace. There are some delays with respect to the original plans (which is quite usual in such extensive projects). The main spectrometer chamber is already partially equiped by the inner electrodes and the external coils which will create the necessary magnetic field. There were some troubles with the provider of the WGTS (windowless gaseous tritium source); in fact they are not completely solved. Anyway, it is sure that the instrument building tends to the successful end, i.e. to the start of the physical measurement.

April 2011: At spring 2011, the already twentieth Collaboration Meeting took place. In Karlsruhe again - naturally, since the whole apparatus is built just there. At present, the equipment of the main spectrometer by the electrodes is practically finished. The pre-spectrometer is being transferred onto its final place at the main spectrometer. As for the tritium source: so called demonstrator - i.e. a body of the tritium source but without the guiding magnets and the active tritium contents - was manufactured. It serves to check the stability of temperatures, pressures, currents etc. After successful tests, it will be returned to the producer's factory where it will be completed to be the full tritium source.

An important event was also the installation of the so called monitor spectrometer. This is a small (about 3 m long) spectrometer of the same type as both the main and pre- spectrometers, which willl serve to ensure the stability of the main spectrometer energy scale. (In fact, it is the original Mainz spectrometer used formerly in the Mainz neutrino experiments. Nevertheless it is substantially renovated and upgraded.)

Similarly as in any great international project, also in KATRIN there are produced diploma and doctor theses as well as other scientific publications. If you are interested to see their (unfortunately incomplete) list and/or texts of most of them, please click here.

An important part of any great project is its popularization. In the Czech media, the following informations appeared: In the Czech TV, October 24, 2005; October 21, 2006 in the newspaper Lidove noviny and October 13, 2006 in the newspaper Pravo (there is no archive available). November 7, 2006, a one hour relation was devoted to the KATRIN project in the Czech radio station Leonardo. (Some relevant photos are here.) On December 4, 2006, another paper on the project KATRIN was issued in the Czech Internet daily 'Nevititelny pes'. On Dec. 8, 2006 - in Lidove noviny again - appeared an information about successful arrival of the main spectrometer to FzK. The same day the station Leonardo broadcasted nine-minute "per phone" interview with O. Dragoun to the same topic.

In 2007, January, there appeared next paper on the project in the journal Akademicky Bulletin. In September, 2007, O. Dragoun has read a lecture in the Institute of Experimental and Applied Physics in Prague. The facts on the program KATRIN as well as a concise history of the neutrino physics were summarized. The text (in Czech) is here. In November (7th a 28th) there were two interviews with O. Dragoun, Will the scientists catch neutrinos? and The neutrino mass, at Czech Radio 3 (Vltava).

In 2008, a next one hour relation took place on the Czech Radio station Leonardo, 28th January. Some days later, Feb. 2, there was a short interview on the Radio Prague about the Czech participation in KATRIN. In March, 2008, O. Dragoun has read an extensive lecture at the Mathematical and Physical Faculty of the Charles University on the development and current status of the KATRIN project. The text of the lecture is here. In the Czech journal Svet, a next interwiev was published "With the physicist Otokar Dragoun on searching, measuring, and influence of the lightest particles in the Universe and on participation of the Czech scientists in the international project KATRIN". At the end of year, Nov. 21, there was another long interview with O. Dragoun on the Czech Radio (in the programme "Duse K") here and an extra "bonus" (What the programme did not accommodate).

In 2011, Jan. 19, there was a twenty minute interview with O. Dragoun and M. Mihaljevic at Czech TV (CT24, program Milenium) on atomic masses and the project KATRIN.

In 2012, Nov. 12, O. Dragoun delivered a one-hour lecture (in the framework of the popularization campaign "Week of Science") Tajuplne neutrino ("Mysterious neutrino").

On Jan. 9, 2013, O. Dragoun read a lecture Současný stav a perspektivy neutrinového experimentu KATRIN ("Present state and perspectives of the neutrino experiment KATRIN") at the Institute of the Particle and Nuclear Physics of the Faculty of Mathematics and Physics of the Charles University.

On Nov. 12, 2013, just one year after the previous lecture (in the same framework of the "Week of Science" campaign), O. Dragoun delivered again a one hour lecture. The lecture had again the name "Mysterious neutrino", but it contents was radically updated. The record of the lecture (in Czech) is here.

Updated Nov. 21, 2013 M. Rysavy You are visitor No.  [CNW:Counter]

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