C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 1 1 RPC gas system slow control (CUHK, 6/10/2009) Changguo Lu Princeton University

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 2 2 Overview Brief description of the Daya Bay Experiment RPC gas system; Signals exchanged between gas system and slow control system: Gas system running parameters; Warning sign; Emergency response; Main building blocks of the slow control screen (just for your reference); On-line operation instruction; Gas chromatograph system: control and database.

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 3 3 RPC Gas System The RPC gas system has five major components: 1.The gas storage bottles, including the bottle changeover system 2.The gas mixing and fire/detector safety monitoring system 3.The gas distribution system 4.The RPCs 5.The gas exhaust system, including the output bubbler system. 6.Not shown in the diagram is gas chromatograph system, which is a standalone system, not interact with other parts of the gas system. (2. and 5. will interact with slow control system.)

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 4 4 Location of the Gas System in the Daya Bay Near Hall (#1) Gas cylinders, ODH & HAD sensors Gas mixing system Host PC for the digital bubbler system (E-room or gas room?) Gas distribution /digital bubbler system crates (total 7) on RPC support frame. USB cable ? ?

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 5 5 Block Diagram of Gas Control and Fire Safety Systems

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 6 6 Logic Diagram of the System Status Crate Fire safety interlock function: If the Emergency Shutoff button is pushed, all four gases will be shut off simultaneously.

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 7 7 Logic Diagram of the Gas Flowmeter Crate The gas flowmeter crate displays the gas flow rate from seven mass flow meters: one for each of the four gases, one for each of the three water-vapor- control branches.

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 8 8 Logic Diagram of the Gas Pressure Crate The gas pressure crate displays the gas pressure at the upper stream of the flow controller for each gas.

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 9 9 Digital Bubbler Microprocessor ADC can reconstruct the bubble shape, the digital bubbler system can count the pulse rate and store the data file in a database.

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 10 Digital Bubbler – Graphics User Interface (Far Hall) 12 bubbler boards, 16 channels/each, display all sub-branches for the Far Hall gas system. Click on any one of the histograms will pop-up a larger histogram window. Bubbling channel Non-bubbling channel On the host PC, the following GUI will be displayed:

RPC Gas System Signals for the Slow Control System The RPC gas system will send signals to the slow control system for on-line monitor and emergency control. Gas flow rate for all four components, the total flow rate, and dry/wet branch flow rates for the gas mixture – Analog signal 0 – 10V and a warning signal on/off. Gas pressure upstream of the mass flow controllers - Analog signal 0 – 10V and a warning signal on/off. Gas mixture humidity – Analog signal 0 – 10V. Ventilation air flow rate – warning signal on/off. HAD sensors – warning signal on/off. Gas cylinder storage room/mixing room temperature/air pressure. (a stand-alone Weather Station device in the gas room). Gas cylinder weights – Warning signal from digital scales (analog signal also available). Emergency shutoff status. RPC HV interlock status, through slow control it should be able to control RPC HV on/standby/off. Gas mixing ratio – Database. Gas bubbling rate for every sub-branch – Database.

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 12 RPC Gas System Signals for the Slow Control System (cont’d)

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 13 What the main building blocks on the GUI may look like All meters and indicators on screen are passive but this Emergency Shutoff Block. If this red light is on, it means the hardware shutoff button has been pushed manually. If for some reason the shift taker needs to push this software button, a warning sign must appear to remind the user the consequence of this action, upon receipt of the confirmation the relevant hardware action takes place.

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 14 On-line operation instruction Gas system has many manual knobs and buttons can be touched, unexpected modification of the setting might cause a lot of confusing to the diagnostic in case of the system warning, it also can interrupt the entire experiment because the gas mix in the RPC system needs long time to be re-stabilized. When the warning sign shows up on the on-line monitoring screen it may cause some panic reaction, thus the on-line instruction to deal with the specific warning could be very helpful. We’ll provide these instructions later, so when slow control group design the system, please make such options available.

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 15 Network configuration for GC system To meet the safety requirement, Isobutane percentage has to be monitored all the time. The upper limit of Isobutane is set at 4.5%. Previous plan was to use InfraRed sensor to measure the content of isobutane in the gas mixture, but the manufacture couldn’t deliver such sensor with the precision we asked for. We gave up this technique, and found an alternative solution – Gas Chromatograph (GC) system. GC is more reliable and accurate instrument, which can measure the mixing ratio for all four components in the mixture with high precision. Daya Bay safety group has approved this method, we are going to place the order for three GCs. There are several ways to operate three GCs. GC is not a simple sensor and it couldn’t be integrated into our present gas control system. They have their own Galaxie Chromatograph Data System (CDS), which has three principle functional components – the Galaxie Main Server, the Galaxie Client and the Galaxie Acquisition Services. To keep the system minimum, we only implement the last one – Galaxie Acquisition Services.

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 16 Galaxie Acquisition and Control Services We want to keep our system as simple as possible, so we choose the configuration on the left. The Galaxie Acquisition and Control Services provide real time communication with all three gas chromatographs. One PC can control all three GCs unless all of them are connected to LAN and assigned IP address. In case of one GC malfunctioning a local PC should be able to take over the control during the debugging.

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 17 Database of the gas mixing ratio This is a temporary database format for the gas mixing ratio, slow control group can set the format and database location, we’ll send the data directly to that location.

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 18 Location of the PCs and interact with slow control We already have one PC at each hall for the gas digital bubbler system, we plan to install the GC Galaxie software into these PCs. These GCs and PCs must be permitted to access LAN. In order to be able to remotely control/monitor the GC system, we also ask for the privilege of the main control PC be able to connect to internet, then we can through remote desktop check the status of the GC system. The measured data (mixing ratio for each gas component) as well as the bubbling rate will be sent to a slow control group created database. Slow control can set a limit on the isobutane safety margin. When the isobutane is over the limit, a warning sign should be issued to remind the shift taker checking the gas system.

C. Lu, RPC Gas Slow Control Workshop, 6/10/2009, CUHK 19 On-line display of the gas mixing ratio The on-line display of the gas mixing ratio on the control PC: