  A clamp pressure cell for neutron scattering experiments at low temperatures
and in external magnetic fields under pressure up to 2~GPa has been fabricated
and tested. The cell provides optical access to the sample space that allows
instantaneous pressure determination during sample loading, cooling and
measuring using ruby and/or samarium doped strontium tetraborate fluorescence
monitoring. A new calibration curve of the pressure-induced shift of the $^7D_0
- ^5F_0$ (0-0) line in the fluorescent spectrum of SrB$_4$O$_7$:Sm$^{2+}$ for
moderate pressures, $P\leqslant{2}$ GPa, is given.
