THE STAR SLOW CONTROLS SYSTEM -STATUS AND UPGRADE PLANS

ABSTRACT The STAR (Solenoidal Tracker At RHIC) experiment located at Brookhaven National Laboratory has been studying relativistic heavy ion collisions since it began operation in the summer of 2000. An EPICS-based hardware controls system monitors the detector's 25000 operating parameters. The system uses VME processors to communicate with sub-system based sensors over a variety of field busses, with High-level Data Link Control (HDLC) being the most prevalent. Other features of the system include interfaces to accelerator and magnet control systems, a web-based archiver, and C++ based communication between STAR online, run control and hardware controls and their associated databases. Planned revisions to the system involve moving I/O controllers from VxWorks to RTEMS; transferring user displays from Sun Workstations to PC's and replacing aging VME processors with PC's. Experience with the existing system as well as upgrade plans are discussed. Proposals for the integration of upgrade detectors are outlined. CURRENT STATUS STAR Overview The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory is home to the STAR (Solenoidal Tracker At RHIC) experiment. The STAR experiment investigates collisions between ions accelerated to energies up to 200 GeV per nucleon. Collisions between polarized proton beams at various energies are also investigated at RHIC. The primary functions of the STAR experiment are the study of nuclear matter at high energy densities and the study of the spin structure function of the proton STAR Slow Controls system The STAR hardware controls system utilizes a Sun Ultra-10 host workstation in the STAR control room running EPICS (Experimental Physics and Industrial Control System) on a network of front-end processors. Control software consisting of the VxWorks operating system, device drivers, control database variables, and user designed control programs resides on the host Sun workstation. Startup commands for an IOC are programmed from the host using either the serial console or the Ethernet connection. When booted the IOC uploads its control software via the network from the host workstation. Any computer on the network that can access the host computer, or any EPICS configured computer on the network can be used to boot an IOC. Once an IOC is booted, failure of the host will not affect the operation of an IOC (unless an IOC is rebooted when the host is down). Since IOC's are only accessible when there is no beam in RHIC, STAR relies on the network to boot/reboot IOC's. In the WAH, the Wiener Crates are connected using a CANbus field bus, with two independent CANbus networks. The EPICS based CANbus control application using CANbus controllers for crate control provides yet a third method for booting/rebooting the electronics in a crate. This design of redundant capabilities to access processors is typical of the slow control design at STAR. The control software of the main workstation utilizes many EPICS host applications and channel access clients to control the STAR subsystems. These applications include the CANbus control application, the Motif Editor Display Manager (MEDM) applications, the sequencer, the alarm handler client (ALH), and the data archiver client. Not all experimental information need during operation is measured by STAR, nor is all the information measured by STAR exclusively used by STAR. For this data, a stand-alone channel access interface, CDEV, is used to exchange data between STAR and the RHIC controls system. All of these applications and programs run on the host workstation. Each subsystem has at least one workstation in the STAR control room on the controls network. These serve as operator interfaces (OPI's) to the control system. During RHIC operation, these OPI's are used for the control of the STAR detector subsystems via their respective MEDM displays. The alarm handler is displayed on the host workstation. Subsystems control displays can be accessed using the alarm handler display. The host workstation has been the development platform for most MEDM display applications. These applications reside on the host in application directories where they are organized along subsystem lines. Currently two versions of MEDM are used to access the display applications. In addition to the subsystem displays, the alarm handler (ALH) display, and CANbus crate control displays also reside on the host. While most IOC's load control software exclusively from the host workstation, some of the subsystems have "system expert only" control software residing on their workstations. This includes DAQ and trigger code. New subsystems have been developed in remote locations and this has led to electronics developers creating their own initial controls systems for testing. A few subsystems have retained these initial pieces of software. One subsystem uses TCL/TK code and displays, which they utilize outside the EPICS MEDM system. A second example is a subsystem that operates its VME crate control outside the CANbus control system. Two of the STAR subsystems have developed complete control systems with independent host workstations on the network. These are essentially mirror images of the primary host workstation, and controls environment. Instead of loading VxWorks, and control software from the primary host, IOC's for these subsystems load software from their respective hosts. These two subsystem hosts run independent MEDM display applications, as well as independent alarm handlers. IOC channels from these subsystems are included in the STAR alarm handler and the STAR controls system host controls the VME crates