Safety Review Document for the Preamplifier System for the T962 LArTPC ------------------------------------------- Rev. Date 16-Sept-2008 This document covers the preamplifier system and its power supplies that are the front-end of the T962 LArTPC DAQ system. The contact person for this equipment is: Dan Edmunds Fermi Phone: x2832 MSU Phone: 517-884-5521 Email: edmunds@pa.msu.edu These preamplifiers are located in the large green "Preamplifier Box" on top of the T962 cryostat which is currently in the main high bay area of the Proton Assembly Building (PAB). In a few months the full T962 system will be moved to a location in the NuMI Tunnel in front of the MINOS Near Detector. The power supplies for these preamplifiers are located in the T962 DAQ rack that is next to the T962 cryostat. The preamplifier cards in the Preamplifier Box are called the PFC-16 cards (Preamp Filter Card 16 channels). In the Preamplifier Box the PFC-16 cards are held in two card files - the upper and the lower preamp card files. Each of these card files has its own Preamp Power Supply chassis and its own Fuse Panel. An overall block diagram of the T962 preamp power system is shown in the following drawing on the web: www.pa.msu.edu/~edmunds/LArTPC/T962/Safety_Review/ t962_preamp_power_block_diagram.pdf The components of this system (given in the order of the power flow) are: Preamp Power Supplies, Preamp Power Cables, Preamp Fuse Panels, PFC-16 cards. Each of these components is described in a section of this note. Preamp Power Supplies --------------------- There are two identical Preamp Power Supplies. The Preamp Power Supplies are located in the T962 DAQ rack next to the T962 cryostat. Each Preamp Power Supply chassis contains 4 separate commercial linear open frame power supplies. A schematic drawing of the Preamp Power Supply is available at: www.pa.msu.edu/~edmunds/LArTPC/T962/Safety_Review/ t962_preamp_power_supply.pdf Each Preamp Power Supply chassis supplies power to 15 PFC-16 cards. The 4 supplies in each Preamp Power Supply chassis provide a total of about 125 Watts of power to the 4 different loads on the PFC-16 cards. The supply voltages and load provided by 15 PFC-16 cards are the following: The +8 Volts supply provides about 3.4 Amps to the PreAmp Vcc load The -6 Volts supply provides about 0.84 Amps to the PreAmp Vee load The +5 Volts supply provides about 9.3 Amps to the Filter Vcc load The -5 Volts supply provides about 9.3 Amps to the Filter Vee load The +8 Volt supply is a Power One model number HE12-10.2-AG linear supply that is rated for 12 Volt output at 10.2 Amps. This supply has been adjusted down to a nominal 8 Volt output by changing a feedback resistor to its uA723 regulator chip and by including two 0.5 Ohm resistors before the bulk DC bridge rectifier to reduce the bulk DC supply and thus reduce the heat dissipated by the 2N3055 pass transistors. The -6 Volt supply is a Power One model number HC5-6/0VP-AG linear supply that is rated for 5 Volt output at 6 Amps. Turning this supply up to a nominal 6 Volt output is accomplished by changing the value of a feedback resistor to the uA723 regulator chip. Even with the output of this supply set to 6 Volts there is still about 4 Volts across its output pass transistor. The light current load on this supply probably contributes to its low noise operation with its output set up to 6 Volts. The +5 Volt, and -5 Volt supplies are Power One model number HE5-18/0VP-AG linear supplies rated for 5 Volt output at 18 Amps. No modifications were made to the +5 and -5 Volt power supplies. All 4 supplies are protected by input and output fuses. The input fuses are located immediately adjacent to each supply. The output fuse of the -6 Volt supply is located on that supply. The output fuses on the +8 Volt and on the +5 and -5 Volt supplies are located in a separate fuse block. The following table shows the values of the input and output fuses. Power-One AC Input DC Output Supply Model Fuse Fuse ------------ ------------ -------- --------- +8V Preamp HE12-10.2-AG 3 Amp 15 Amp -6V Preamp HC5-6/OVP-AG 1 Amp 3 Amp +5V Filter HE5-18/0VP-AG 3 Amp 15 Amp -5V Filter HE5-18/0VP-AG 3 Amp 15 Amp There are separate front panel indicator LEDs and tip jack test points for each of the 4 supplies. These components and wiring are protected by separate 3 Amp pico fuses. The +8 Volt and the +5 and -5 Volt DC outputs from the Preamp Power Supply chassis are provided by terminals on a large fuse block. The return terminals and the -6 Volt output terminal are provided on a Wieland terminal strip. These terminals are rated all rated for 30 Amps. Each Preamp Power Supply is interlocked with the cooling air blower for the Preamplifier Box. When the air blower is running it provides a low current 12 Volt control signal to each Preamp Power Supply chassis that closes a solid state relay and thus allows AC line power to reach the Preamp Power Supply. When the air blower is off then all AC power is blocked from reaching the Preamp Power Supplies. The solid state relay that is used in the Preamp Power Supply chassis is a Crydom model CWD2425S that is rated for 240 VAC and 25 Amps. The green-yellow safety ground wire in the Preamp Power Supply AC line cord is not tied to the Preamp Power Supply chassis. Rather the Preamp Power Supply chassis is tied to the T962 cryostat via #10 AWG wire and lugs. In turn the T962 cryostat is connected to the PAB building ground with 3/4" copper braid. More information about the T962 Preamp Power Supply chassis is on the web at: www.pa.msu.edu/~edmunds/LArTPC/T962/Preamp_Filter_Power_Supplies/ preamp_power_supply_description.txt A picture of the T962 Preamp Power Supply is available on the web at: www.pa.msu.edu/~edmunds/LArTPC/T962/Preamp_Filter_Power_Supplies/ Pictures/power_supply_front_above.jpg The DC output from each Preamp Power Supply chassis is carried over to the Preamplifier Box on the T962 cryostat by a Preamp Power Cable. Preamp Power Cable ------------------ The Preamp Power Cable is about 25 ft long and carries the DC power from a Preamp Power Supply chassis over to either the upper or lower section of the Preamp Box on the T962 cryostat. This power cable is shown in the following schematic drawing on the web at: www.pa.msu.edu/~edmunds/LArTPC/T962/Safety_Review/ t962_preamp_power_cable.pdf This cable carries power to 2 different sections on the PFC-16 cards. The sections of the PFC-16 cards are the "Pre-Amplifier" and the "Filter". Each of these sections uses a Vcc and a Vee supply. There are 4 wires in the power cable for each section: a Vcc wire, a Vee wire, and two return wires. All of these wires are 14 AWG with 105 deg C insulation. Each set of 4 wires is twisted together. There is a woven plastic sleeving around the overall cable. At the Preamp Box end of the cable there are 2 Cinch-Jones connectors, one for each section. The Vcc and Vee supply for each section are carried on one contact of the Cinch-Jones connector for that section. The return lines for that section are carried on two contacts and the alignment pin of the connector. Each contact of the connector is rated for 15 Amps. A picture of the Preamp Power Cable is available on the web at: www.pa.msu.edu/~edmunds/LArTPC/T962/Preamp_Filter_Power_Supplies/ Pictures/power_cable_to_preamp_box.jpg Preamp Fuse Panel ----------------- At the Preamp Box the DC power is received on 2 Cinch-Jones connectors. From these connectors the power runs over to a fuse panel through 14 AWG wires. This #14 wiring is setup the same way as in the Preamp Power Cable. There are separate Preamp Fuse Panels for upper and lower card files in the Preamp Box. Each Preamp Fuse Panel receives power from one Preamp Power Supply chassis and delivers power to 15 PFC-16 cards. Each Preamp Fuse Panel has a section for the Vcc and Vee Preamp fuses and a section for the Vcc and Vee Filter fuses. The Preamp Fuse Panel is shown in the following 2 drawings. All of the parts are mounted on one panel but 2 drawings were used for clarity. www.pa.msu.edu/~edmunds/LArTPC/T962/Safety_Review/ t962_fuse_panel_preamp_section.pdf t962_fuse_panel_filter_section.pdf Each Preamp Fuse Panel has fuses and output cables to supply power to 15 PFC-16 cards. There is a 2 1/4 Amp fuse in each of the 4 supply voltages that go to each of the PFC-16 cards. The cables that carry the power from the fuse panel to each PFC-16 card are made with 22 AWG wire. Each PFC-16 card has one cable for its "Preamplifier" power and another cable for its "Filter" power. The connectors that plug these cables into the PFC-16 cards are make with 6 position AMP MOD IV housings and AMP high pressure contacts. The contacts are AMP/Tyco part number 1-87309-4 Newark stock number 90F3791. These contacts are rated for 3 Amps each. The current rating specification for these contacts is available from AMP/Tyco web site at: http://catalog.tycoelectronics.com/TE/bin/ TE.Connect?C=1&PN=1-87309-4&M=BYPN&LG=1&I=13 The following picture on the web shows one of the 2 Preamp Fuse Panels before it was installed in the Preamp Box. www.pa.msu.edu/~edmunds/LArTPC/T962/Preamp_Filter_Power_Supplies/ Pictures/lower_fuse_panel_full.jpg PFC-16 Cards ------------ The PFC-16 cards receive "already fused power" on 2 connectors. Each connector is a 6 pin header of 25 mil square pins. One connector is for the Preamp power and the other connector is for the "Filter" power. Once the power is on a PFC-16 card, the card is protected from spikes and reverse polarity by a Transient Voltage Suppressor on each of the 4 supplies. Each supply is also cleaned up by bulk Aluminum Electrolytic and Tantalum capacitors before they reach the actual electronics components on the card. The PFC-16 card can been seen in the following picture on the web. You can see where the power is received on the PFC-16 card along the left-hand edge in this picture. www.pa.msu.edu/~edmunds/LArTPC/T962/Preamp_Filter_Card/ pict_pfc_16_card.jpg The power connectors on the PFC-16 card are rotationally symmetric, i.e. if one is plugged in rotated by 180 deg it makes no difference. If a connector is plugged in offset by one pin then it will directly short circuit the supply and blow the 2 1/4 Amp fuse (the card itself will not see any significant supply voltage). If the connector for the Preamp supply is exchanged with the connector for the Filter supply nothing is damaged. The PFC-16 card will not work well with these connectors interchanged but nothing is damaged. Gerber files of the layers on the PFC-16 card that carry power can be made available for review. The power is carried on power planes so there is not really an issue about sufficient trace width to match the 2 1/4 Amp fuses that protects the card. Each PFC-16 card has 4 banana plug pins that connect the ground plane of the card to the cryostat vessel which is the signal ground for the LArTPC signals. You can see these banana plugs in the picture of the PFC-16 card. It is only through these banana plugs the the Preamp Power Supply return lines are tied to ground.