In 2012 the main activities of the MUEXC collaboration can be summarized as follows:
a) Maintenance of the cryostat. After the evaluation of the damage to the PRESS-MAG-O system due to mishandling during a transfer inside the LNF an order to the DG-Technology, the company that realized the system, has been emitted to fix damages occurred to the cryostat. Moreover, operation, reliability and safety of the superconducting magnet have been tested by the manufacturer of the magnet: the AMI Inc. in USA, where it has been control the superconducting switch of the magnet and has been energized with currents up to 100 A (corresponding to a maximum value of 7 Tesla). Regarding the cryostat, before the end of the year begins the reassembling of the system to make possible vacuum tests and later operations at low temperature.
b) Operation of the PRESS-MAG-O insert: we proceeded also the final commissioning of the PRESS-MAG-O insert. The heart of the system is a SQUID gradiometer designed and manufactured to operate inside the Diamond Anvil Cell (DAC) with a SQUID amplifier placed on the bottom of the insert. Several measurements have been performed to test the gradiometer operation at 4.2 K with a superconducting sample (a YBCO sample of dimension ~0,16 mm3) loaded in the DAC cell. To remove noises due to the interferences of RF signals we shielded the SQUID signals with a box made by ferrite RF filters and capacitors. Different measurements have been performed to set the procedure and the suitable experimental set-up for susceptibility ac multi harmonic experiments using the instrumental chain formed by a Sinusoidal Pulse Amplifier and an AC Current Amplifier that control the magnetic field excitation and the SQUID-gradiometer, the Lock-In amplifier that measure the magnetic signal of the superconducting coils sets inside the DAC cell. The procedure optimizes: 1) the functionality of the SQUID maximizing the response with a signal test generated by the SQUID system. At first we use a sinusoidal test signal of 6 mV at 107 Hz corresponding to ~12 mGauss that give a pick-up signal of 15 flux quanta, 2) the AC exciting magnetic field starting with an amplitude of 12.8 mV corresponding to 25.6 mGauss at 107 Hz frequency to test the linear response of the SQUID, 3) the Lock-In amplifier signals of the SQUID that pick-up the superconducting gradiometer. In the figure we show values read from the lock-in for the first and third harmonics at 4.2 K, 107 Hz and 25.6 mGauss. We carried out also measurements at different values of the frequency (17-1070 Hz) and of the AC magnetic fields (10 mGauss-10 Gauss) always at 4.2 K. The SQUID-gradiometer showed a high sensitivity working at magnetic fields excitation of the order of mGauss. For magnetic fields greather then 1 Gauss attenuators have to be inserted to probe the magnetic response with the Lock-In amplifier.