The following potential hazards have been identified:
The system is supplied by 220Vac and 110Vac and there is a magneto-thermic and differential switch at the very first entrance of the power supply. All the lines at these voltages are kept inside the racks, and the plugs satisfy the european CE rules for these voltages. The supply for the single devices inside the racks are all at 5VCC, 12VCC, 24VCC, but for the pump which needs 110VCC and for the Motor Drivers, which needs a special 80VCC voltage. A custom power supply unit has been built for this purpose, and this unit is kept in the so called "Power Supply Unit" at the bottom of Left Rack, together with the other supply units. The signal lines are low voltage (<=12VCC the digital lines, 0-5V or 4-20mA loops the analog ones) and kept separated from the supply lines by using different connectors and separated cables. Optocouplers have been used for the microswitch line-in, isolated input lines have been used for the analog lines. A potential hazard outside of the Racks, are the motor cables, which must be touched only by AUTHORIZED PERSONNEL and with power supply switched off.. An 80VCC/2A (square wave, duty cycle 0,5) current flows in these cables when motors are in stand mode, this current grows up to 7A (square wave, duty cycle 0,5) when motors are moving; these high power lines are everywhere kept separated from the low voltage lines . The pump power supply line is kept inside of the Racks, and in a position that cannot be reached unless opening the side panel of the Right Rack.
This system has potential hazard only if hydrogen is used. The volume is 10 liters. The pressure is 1.02 atm. The cell gas tightening has been tested up to 2 bars. The tubes are made of stainless steel, 6 mm in diameter. The electro-valves are anti-deflagrant according to the USA regulations, working at low voltage (24V AC). All the power supplies for this section are kept separate in a different rack.
The default value for the valves, which is the rest position if power supply fails, is "closed". Regulating the pressure on the gas cylinder to 0.2 Atm avoids that the pressure in the target cell override this value also in the case of failure of any valve. Both the manual valve command and the remote valve command, from the calculator, need that the operator keeps the valve open by keeping pressed the corresponding button (from the computer: keeping pressed the mouse button on the corresponding button icon); if this button is left, unpressed the valves go back to their default value, which is, as said, "close". Any leakage from the cell would be immediately detected by the scattering chamber vacuum measuring system.
Leakages outside of the scattering chamber should spill in the surrounding atmosphere of the HallA but, because of the small amount of gas spread around, caused from the small gas overpressure, this does not represent a potential hazard fot the people working around in the hall; anyway, there are two pressure transducers in front of Right Rack, and their values can be seen from the HallA, directly on the panel, as far as from the Counting Room, because one of the devices is acquired by the calculator. Moreover, there is a camera, pointing at those displays, and whose monitor is the Counting Room; these devices realtime show the pressure, and immediately reveal if, somewhere in the circuit, there is some leakage.
There are about 17 liters of pure water in the circuit. The water tank, the tubes, the target and the cell containing it, are made of stainless steel. The tubes are joined by "swagelok" connectors. The beam passes through two windows, which are made of Be(75 micron thickness); the other two windows are made of kapton.
The cell gas tightening has been tested up to 2 bars. No water leakage is expected except in case of breaking of the windows of the target cell. In this case some water, carrying some radioactivity, goes into the scattering chamber.
The calculations performed by Geoff Stapleton (see Appendix) shows that radiological precautions necessary are rather low. The water should not be leaked into the hall drains. Measurements at convenient intervals will be made by the radiation control group on samples, to permit determinations of the radionuclides yields. In the case of water loss or the need to drain the water, the radiation control group has to be informed to permit precautionary measurements. The cooling unit allows to mantain, by a heath exchanger and a termostat, the wanted temperature (15-20 degrees Celsius).