Alexander Petoukhov

by Eddy Lelièvre-Berna

After a brilliant start of his career in Gatchina (Russia), Alexander Petukhov (Sasha) came for the first time to ILL in 1996 to successfully measure the spin rotation without parity conservation in Lanthanum on D3. This was one of the very first experiments performed with a ³He spin filter developed by Francis Tasset and collaborators.

During the two following decades, in the Neutron Optics group of the ILL, he actively participated in the development of many optical components for polarised beams. He first designed magnetostatic cavities for maintaining the ³He polarization: a detector including polarization analysis installed on the diffractometer D3 and two boxes for transporting easily spin filter cells from the filling station to the instruments. These boxes were called MagicBox because the field homogeneity was slightly better than the calculated one. He then helped us build a RF adiabatic flipper with 99.9% efficiency down to 0.42 Å and adiabatic fast passage flippers to reverse the ³He polarization.

He then contributed a lot to the evolution of PASTIS: an insert for polarization analysis studies on a thermal inelastic spectrometer, installed today on IN20. This insert allows to perform polarization analysis for any direction of the magnetic field at the sample position with ³He neutron spin polarizer, a ³He spin flipper and a ³He wide-angle neutron spin analyzer [1]. An extended version for time-of-flight spectrometers is also in construction. Last but not least, he proposed a new concept of broad-band solid-state polarizer [2] and participated actively in the construction of the new polarizer of PF1B.

In parallel, in the Nuclear and Particle Physics group, he contributed significantly to the discovery of quantum gravitational states of the neutron [3], to precision measurements of the weak interaction in neutron decay and neutron-nucleus interaction, to the discovery of asymmetries in the emission of ternary particles in nuclear fission and to the development of very sensitive diffraction enhanced particle-physics experiments. The measurement of the neutron electric dipole moment via spin rotation in a non-centrosymmetric crystal with the Cryopad was a great venture.

References
[1] D. Jullien et al., Nuclear Inst. and Methods in Physics Research A 1010 (2021) 165558. DOI: 10.1016/j.nima.2021.165558
[2] A.K. Petukhov et al., Nuclear Instruments and Methods in Physics Research A 838 (2016) 33-38. DOI: 10.1016/j.nima.2016.09.023
[3] V.V. Nesvizhevsky et al., Nature 415 (2002) 297-299. DOI: 10.1038/415297a