To further interpret the XPS results obtained for the polarizing treatment of PVDF films, each sample was characterized individually.
higher net dipole moment after polarizing treatment, which is greater in polar crystalline regions of polymer compared to nonpolar regions including amorphous phase.
It can be seen that the ferroelectric property of PVDF films was slightly dependent on different polarizing treatments.
The variation of different bands in IR spectrum provides important information about the phase transitions of PVDF films treated by different polarizing treatments .
The vibrational bands at 880 [cm.sup.-1] (skeletal vibrating and C[F.sub.2] vibrating), 840 [cm.sup.-1] (C[H.sub.2] rocking), and 510 [cm.sup.-1] (C[F.sub.2] bending) are detected, which indicates the samples after polarizing treatments comprise of polar [beta] crystalline phase.
It seems that at higher poling electric field, scission reaction (free radical formation) took place to cause the increase in molecular mobility and induce polymer molecules from the amorphous region to crystalline or other crystalline phase to polar [beta] crystalline phase during the polarizing process.
The second characteristic parameter is the polarizing (analyzing) efficiency [P.sub.n] and thus also the resulting neutron polarization which can be expressed by
We are polarizing the [.sup.3]He gas by Metastability Exchange Optical Pumping (MEOP) where the atoms from the ground state are excited into the metastable [2.sup.3][S.sub.1] state by a discharge and can then be pumped by a 1083 nm-Laser.
The polarizing and compressing system consists of three parts:
Yury Sobolev are mainly involved in neutron physics and Marion Batz, Daniel Rudersdorf, Jorg Schmiedeskamp and Michael Wolf are doing their PhD-thesis working on MEOP and the polarizing and compressing system.
The beam polarization after the [.sup.3]He spin filter is [P.sub.n] = tanh(t/[tau]), [tau] = L/[[P.sub.3][[rho].sub.3]l[[sigma].sub.1][v.sub.1]], l is the cell length, [[sigma].sub.1] is the polarizing
cross section at the neutron velocity [v.sub.1], L is the flight path length, [[rho].sub.3] in the number of [.sup.3]He atoms per [cm.sup.3], and [P.sub.3] is the [.sup.3]He polarization.
This scheme allows the full power of the laser to be incident on OPC2, and can be constructed without the use of large area polarizing optics.
There are several critical requirements on the compressor: 1) an inlet pressure on the order of 0.1 kPa at throughputs comparable to the polarizing rate for the metastable method; 2) sufficiently low leakage and permeation from the ambient atmosphere and outgassing of wetted compressor materials (ie., materials the gas contacts), 3) construction from non-magnetic materials so that the uniform magnetic field is not distorted, and 4) wetted materials that do not cause excessive depolarization during the time the gas is in the compressor.