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L.Gatignon 19 February 2008 P42+K12 User Guide 1. Introduction The P42+K12 beam is a complex of beam lines that serves the NA62/P326 detector located in the ECN3 underground experimental area. The P42 beam transports charged particles from the T4 primary target, located in the primary target area TCC2, to the T10 target. The K12 beam transports the particles from T10 to the experiment. The operation of the P42 and K12 beam lines is done using the Cesar application program, which is common to all North Area beam lines. The general features are described in a separate document, which the reader is supposed to be familiar with. This document describes specific features of the operation of these two beam lines. 2. The P42 beam The P42 beam is normally operated as a primary proton beam that transports the protons traversing the T4 primary target in TCC2 to the T10 target, located 838 meters further downstream in the TCC8 area. From there on secondary particles are transported into ECN3 by the K12 beam. The transmission of the beam is controlled by two dump collimators, TAX1 and TAX2, which each offer a series of holes with different diameter, allowing a reduction of the beam flux onto T10. For very low rates, two holes are filled with 40, respectively 80 cm of Beryllium. Only if those Beryllium-filled holes are used, the beam flux may be further adjusted with the standard 4-jaw collimators, installed all along the beam line. Exceptionally the P42 beam is set up as a very pure and high-resolution electron beam or as a secondary high-energy hadron beam. To reduce the risk of damage to beam and/or experiment equipment, the changes from one mode to another are normally done by the AB/ATB/SBA beam line expert. Please note that for electron beams the converter must be IN, whereas fore all other modes the converter MUST be OUT. The other changes are magnet and collimator settings defined in the relevant beam files. Please note that Bend 1 of the P42 beam is the same physical magnet as Bend 3 of the T4 wobbling station. In order to avoid accidents and misunderstandings, Bend 1 is NOT part of the P42 beam files. However, its status can be read and its values changes by the standard Cesar GUIs for the P42 beam. A tuning procedure is available, as well as the beam optics. The nominal currents are collected in the appropriate beam files. Normally it is sufficient to regularly check the magnet currents (via magnet status) and TAX positions (via Dump status) and the T10 intensity on the Page-1 TV screen. To adjust the T10 flux slightly, please call the SPS operators. The currents in the main bends of the P42 beam line are monitored by the P0-Survey system that closes TAX-1 of P41 and P61 in case a bend id out of tolerance. See section 6 for more details. 3. The K12 beam The K12 beam is designed as a secondary beam that transports simultaneously positive and negative hadrons of the same nominal momentum from the T10 target towards the P326 ("NA48/3") experiment located at the end of ECN3, some ~ 240 meters downstream of T10. The active elements of the K12 beam are located within the first 120 meters, except the spectrometer magnet MNP33. The charged secondaries produced in T10 are momentum separated by a first achromat, consisting of 4 identical magnets, connected in series as Bends 1 and 2. In between the second and third of the magnets the beam is parallel to the central beam axis, but displaced vertically as a function of particle momentum. For the nominal momentum, 75 GeV/c in 2007, this displacement is 100 mm. The combination of the two TAXES allows to define an aperture that defines the wanted momentum band. If so required, one of the two beams (or both) can be blocked in the dump collimators K12-TAX 1 and 2. At the exit of the first magnets the charged beam(s) is (are) back on the central axis. A short section of beam allows to clean the beam from halo particles (hadron tails via the XCLD cleaning collimators, muon tails by the muon sweeper Bend 3) and to focus onto the experiment. This section is followed by a second achromat (beam excursion only 40 mm) that houses an optional spectrometer ("KABES"), which is not in place during the 2007 run. This achromat is then followed by two magnetic collimators (Scrapers) for additional muon cleaning and a final collimator. The beam then enters the blue decay tube of the NA48 apparatus. A final beam diagnostics station is located at the very downstream end of the experimental hall, just behind the last NA48 detectors. For certain tests, the beam is made ~parallel at the location of the straw detectors (in the upstream part of the blue vacuum tank) or at the RICH prototype (upstream of the blue tube). These changes are basically managed by specific beam files. In case a secondary hadron or electron beam is transported directly from the T4 target to the experiment, the T10 target head must be taken out („head 0‟) via the Obstacles Status task button or menu. Often muon beams are required. These are made by closing both K12 taxes at +140 mm and by switching off the muon sweepers (BEND-03 and the SCRapers) and the second achromat, as well as all quadrupoles and MNP33. Again this is managed via the K12 beam files. The change from one mode to another is usually done by or in close cooperation with the beam physicist. It is very important to make sure that the beam is stopped during the intervention and that the P0-Survey system is managed correctly (see section 6). If not, one may accidentally destroy the experiment! Some of the K12 magnet currents are also monitored by the P0-Survey system. Some tuning instructions are available in a separate page. Also available is the beam optics. A quick check of the correct functioning of the beam consists of checking the T10 flux, the experimental scalers and the profile on K12-MWPC1+2. 4. The MNP33 spectrometer magnet The MNP33 spectrometer magnet is rather special in at least two respects: - it consumes a significant amount of power, ~ 2 MW DC - it has two independently powered coils with two coupled rectifiers, the current ratio being exactly 2.0. The coils are powered via BEND06 and BEND07. The control can be done using the standard rectifier status panel, but the sequence of operations is long and tricky. To make life easy a special program has been made available from the menu EA → MNP33 control, only accessible from the K12 work space. Please enter the required current and the program will take the rest. However, as the ramp is slow, the process may take several minutes. Beware that MNP33 (in fact K12-BEND06) is normally surveyed by the P0-Survey system (see section 6). Any change of current will stop the beam (by closing a TAX), except if appropriate measures are taken w.r.t. P0-survey. The degaussing of MNP33 must be done „by hand‟, i.e. by setting a sequence of currents according to the procedure described above. The sequence is +1200, -900, +600, -400, +200, -100, 0 Amps. 5. Dump Control In case the P42 beam lines runs in high-intensity primary proton mode, the T10 target and TAX must be water cooled to avoid damage. A hardware surveillance system, called dump control (DMPC), will close TAX-1 of the P41 and P61 beam lines in case of such a cooling problem. Two additional channels are entered in this system as well: P0-Survey (see section 6) and radiation monitors. The TAX can only be reopened after the problem has been solved (ask the SPS operators if you cannot solve it yourself, by e.g. starting a magnet) and the dump control has been RESET. The whole system is (de-)activated via the DUMP control suite, accessible only from the P42 workspace via the EA → P0-Survey menu. The third tab, labeled “DMPC” allows the reset. Please do not disable any of the channels under any circumstances without prior approval by the beam line expert (Lau Gatignon)! 6. P0-Survey In view of the high beam intensities, it is normally necessary to monitor the magnet currents in the main bends. The P0survey software, running in the POWJC front-end, checks whether any current is out of tolerance (typically 1 Amp) with respect to a special surveillance reference. If this is the case, TAX-1 of P41 and P61 are closed. The alarm is memorized and the TAX can only be opened once the alarm has been reset. The status of P0-SURVEY and a reset, as well as configuration tools (the latter only to be used by the EA physicists) are accessible from the console manager. The whole system is (de-)activated via the DUMP control suite, accessible only from the P42 workspace via the EA → P0-Survey menu. The ENABLE/DISABLE of P0-survey is normally only done by the EA physicists. The users and operators should not disable the P0 surveillance, only RESET the alarms. The configuration of P0-survey can be done from two places: 1. from the console manager in the CCC via SPS EA operations - P0 Surveillance 2. from the P42 workspace in CESAR via the EA menu, option P0Survey. This opens a threefold panel, selectable by tabs. The STATUS panel shows the magnet name, the current in each magnet, the beam reference, the surveillance reference, a tick whether the surveillance is preselected for this magnets and whether this magnet generates an alarm for the system. The lines are shown in red if the current or beam reference is out of tolerance with respect to the P0SURVEY reference. Normally the alarm box should also be ticked (if the element is selected for surveillance); if not there is a problem with the P0survey system. The status panel does not allow actions. The CONFIGURATION panel requires expert privilege and shows the beam reference current, P0 reference current and tolerance for each magnet, as well as a checkbox to preselect or not each magnet for surveillance. A special checkbox above the table allows selecting all magnets for surveillance. The list of reference currents and tolerances are stored in P0Survey files. Different P0Survey files can be loaded from the selector box at the top. Alternatively (and typically) the EA physicist copies the beam reference settings into the P0 reference current values. All P0-surveillance currents and tolerances are editable. Once the EA physicist is happy with these values, he can save the surveillance references and tolerances into either the active file or into a new file (called P0SURVEY.xxx). Once these settings have been saved, he can SEND them to the equipment. This updates the reference currents and tolerances, but not the currents themselves, nor the beam references! The P0-SURVEY system is activated by the DMPC panel. The EA physicist can enable or disable the system as a whole. If the system is disabled, no alarms will be transmitted and the TAX will not be closed. Every user may RESET the alarms, which is a necessary condition to open the TAX. The DMPC panel also allows enabling or disabling three other alarm sources (T10 water, T10 TAX cooling and radiation alarms). All three should always be enabled. If one of them gives an alarm, the equipment giving the alarm should be repaired or reset and the DMPC alarm reset. Please note that the End-of-access program for ECN3 also resets P0-Survey alarms after having switched on the access bends and before the TAX are (can be!) opened. In case this 'automatic' reset fails, the DMPC panel should be used to RESET all alarms and the TAX opened manually from the appropriate Cesar panel. 7. Access to ECNS and other beam areas Access to ECN3 or its associated galleries requires that the beam is put in a safe condition to avoid radiation exposure of the personnel entering these areas. The access to ECN3 and all other galleries except GL300 require TAX1 and TAX2 in P41 and P61 to be closed, as well as BENDS 4, 5 and 6 of P42 to be OFF. This condition is prepared by the Access Command task button for zone ECN3 or the gallery in question (e.g. PPE853 or PPE854). Wait for the program to finish its action and ask the SPS operators to disable Chain-16. After the access, when all keys are back, ask the operators to enable Chain-16 and run the Access Command program again to switch on the beam. Access to technical gallery GL300 requires TAX-2 of P42 to be in SMALL SELECTED RANGE, which implies a reduction of the proton flux of T10 from nominal by a factor of 6. This condition is prepared by the Access GUI for GL300 and monitored continuously by the EA implementation of the SIS system. The END OF ACCESS program for GL300 sets the range back to MEDIUM, but the TAX position must be set by the user. 8. Final remarks There are many reasons why the beam line may stop to work. Useful things to check are the following: - Check on the Page-1 screen whether there is beam on T4 and T10. - Check the magnet currents in P42 and K12 and correct, if necessary. - If there is beam on T4 but not on T10, please check the TAXes of P42 - If P42-TAX1 is closed, DMPC or P0-SURVEY may have tripped. Check and correct. - If P42-TAX2 is closed, possibly a wrong manipulation has been done with access to technical gallery GL300. Please close the gallery and open the TAX again. If everything else fails, call the SPS operators at 77500 (24/24) for operational questions or, during reasonable hours, the beam line physicist (Lau Gatignon) at 163554.
"K12 User Guide 2008"