The Equipment for Forming the Polarized Neutron Beam at Channel 51 of SINQ

The equipment to form the polarized neutron beam for fundamental investigations at channel 51 of SINQ PSI (Switzerland)

The equipment for a polarized cold neutron beam of sector 50 at SINQ was created by common efforts of Petersburg Nuclear Physics Institute (Gatchina, Russia) and Paul Scherrer Institute (Villigen, Switzerland). The equipment is intended for formation of a polarized cold neutron beam for joint fundamental studies in the field of nuclear physics.
The equipment was worked out with due regard for the restricted area for installation of the polarizer and the filter of gamma-quanta and fast neutrons. The system of polarization and filtration includes multichannel mirror polarizer , multichannel mirror bender and mirror condenser. These three mirror units for the beam formation serve as a deflector which deviates the beam of cold neutrons out of the direct view of the cold neutron source and provides filtration of the cold neutron beam from gamma-quanta and fast neutrons. The equipment includes also an analyzer of the beam polarization.
The Design is based on the experience of PNPI in production of polarized cold neutron beams of high flux density and multichannel neutron guides on the basis of polarizing CoFe/TiZr and non-magnetic NiMo/Ti supermirrors with m=2 (by definition, the effective critical reflection angle of a supermirror in m times exceeds that of Ni). The experience of PNPI in production of analyzers has been put to good use, too. The Design is based also on the experience of PSI in development of Ni/Ti supermirrors with m=2 and m=3.5. The main parameters of the Tract Units are represented in a table.

**The main geometrical parameters of the polarizer with a condenser**
Element	beam cross-section (mm²)	length (mm)	channel width (mm)	deflected angle (rad)	number of channels	glass thickness (mm)	vertical wall coating	horizontal wall coating
Polariser	80x150	800	2.0	0.0273	34	0.4	FeCo/TiZr (m=2)	-
Bender	80x150	800	2.0	0.0273	34	0.4	Ni/Ti (m=2)	-
Condenser	80x150	4000	80.0	0.0	1	5.0	Ni/Ti (m=3)	NiMo/Ti (m=2)

The general view of the
mounted equipment.

The view of the multichannel
polarizer from the side of the
neutron source.

Calculated and measured spectral distributions of the neutron flux density.

Calculated and measured spectral dependence of the neutron beam polarization.

The top and side views of the equipment for forming the polarized cold neutron beam at SINQ:

the neutron guide with the supermirrors Ni/Ti;
the shutter;
the polarizing bender with supermirrors CoFe/TiN and FeCo/TiZr;
the 6 Li-doped plastic shutter;
the condenser with non-magnetic supermirrors NiMo/Ti;
the radiofrequency spin flipper;
the moveable truss;
the beam;
the external shielding.

The cross sections of the polarizing bender (A-A), the condenser (B-B) and the spin flipper (C-C):

CoFe/TiN and FeCo/TiZr supermirrors (1), the iron spacers (2), the titanium stencils (3), the stainless steel vacuum jacket (4), the magnetic vacuum system with ferrite elements (5), the blocks of the stainless steel shielding (6), the optical section (7), the boron plastic (8), the iron vacuum jacket-magnetic conductor (9), the radiofrequency coils (10), the magnetic system of the spin flipper(11).

User:

Contact person: Prof. Ralph Eichler,
Head of Particles and Matter Dept.
CH -- 5232 Villigen PSI, Switzerland
Phone: + (41) 563103216
E-mail: Ralph.Eichler@psi.ch