OSP Hall A - Jefferson Lab
Contents
1. Table 3 5 List of HRS responsible personnel where W B stands for the white board in the counting house 3 8 Spectrometer Rotation Since each HRS weighs in excess of 1 000 tons it is very important that all safety precau tions are carefully adhered to The good news is they move very slowly a few degrees min maximum BUT 1 000 tons moving even very slowly is hard to stop 3 8 1 Hazards Hazards include e Knocking items over e The wheels crushing things including fingers and toes on the floor in the path of the spectrometer e Damaging the beamline or other equipment on the floor if one goes to too small or too large an angle or if it just gets pushed around inadvertently e Tearing out of cables etc physically attached to the superstructure 3 8 2 Mitigations Hazard mitigations e Guards on either side of the wheels prevent items from getting under them e Large pins in the floor to stop the spectrometer rotated beyond the needed angular range e Blinking lights on the spectrometers indicating they are in motion or that motion is possible controls engaged etc CHAPTER 3 HALL SPECIFIC EQUIPMENT 20 e During a running experiment the run coordinator and work coordinator should know in advance of any moves Moves at any other time must be cleared with the Hall work coordinator before implementation e Careful inspection of the intended path to make sure it is clear This is part of the pre run checklist p2. Experiment Safety Assessment Document ESAD for Experimental Hall A Base Equipment February 2 2015 Contents 1 Introduction 3 2 General Hazards 4 A 4 Coe EM rr rar OES wR OES oe OH eee ee eS 4 26 Electrical Bynes soo ns es a ek ease bees Pe dweadk wei 5 24 Mechanical Systems sc cos ee AR A SEE RB 5 20 Strong Magnetic Fields ocioso he eae dea eR Eee ee 5 2 6 Cryogenic Fluids and Oxygen Deficiency Hazard 5 2 7 Vacuum and Pressure Vessels dea ew hb ede Re SORA Ee ER 6 29 Hazardous Valedor ewe OB RSS 6 29 ARS ciar SOs Ee Oe EOE RS ARA RRS 6 3 Hall Specific Equipment 8 ik VO oe bg Hh cee 2p BO ee A ee eK OR eK es 8 3 2 Checking Tie in To Machine Fast Shutdown System 8 ie Beamline ass e as a eS Be eiw a ene a a ee Ah eR BG 8 Duel Hazardg e mica ee Oe E te ER Ge ee Se ia 9 eee NUNES 222 e bE eH Ree eee ee Oe Se eS 9 3 3 3 Responsible Personnel osas 8 oR ea GS we eee eS OR 10 3 4 Are Energy Measurement 5 4 0464664 pe ees Fed ee a ws 10 eee PROS O ok A ee a ai 10 La NUINESUODS 4 soriana de E wee ee RRS 10 34 3 Responsible Personnel o ses scsi ba eh Ya haha owe 11 ao Cryogenie Target Syste lt s c toea s soi a e a a a e 12 al Hazarda cosas ra A 12 Al DIMAS ca oss ai edas Sk a Se EMEPE SERED i 12 3 03 Responsible Personnel orei tce ra tak Dee EEE RES 15 20 VAIO a si ok he arice dr o aiai 17 O AA aci ia ir Do A 17 20 2 Mitigations sidra ridad 17 3 6 3 Responsible Personnel lt e
3. 3 5 Cryogenic Target System The Hall A cryotarget system allows for multiple configurations depending on the re quirements of the experiment s In the standard configuration the system has three separate target loops One of these loops contains low pressure He gas with pressure up to 32 psia The other two loops are usually used for liquid hydrogen and deuterium targets Each loop can have one or two target cells which is again dependent experiment requirements Below the loops solid targets such as carbon foils can be added A short version of the cryotarget target control system user manual is available at http hallaweb jlab org equipment targets cryotargets Halla_tgt html An updated User s Guide to the Hall A Cryotarget is available at https polweb guides atarg ATARG_MAN html Other useful information for cryotarget operators is also avail able at the above web sites It is mandatory to have an alarm handler ALH running at all times when the target has been cooled down Further it is mandatory that the alarm handler be visible in all work spaces on the target control computer Even though the target safety is ultimately insured by mechanical measures the alarm handler can save you lots of time grief and potentially prevent problems with data The ALH will alarm if any of its parameters goes out of normal range Servicing the alarm is the responsibility of the target operator At high beam current the ALH will usually alarm when
4. A 7413 jpchen jlab org Cryotarget Greg Smith Hall C 5405 smithg jlab org Cryotarget Silviu Covrig Hall C 6410 covrig jlab org Cryotarget JLab Cryo Target Group Dave Meekins Physics 5434 meekins jlab org Christopher Keith Physics 5878 ckeith jlab org Central Helium Liquefier CHL Experts Cryo on Call via MCC 7048 ESR CHL group Cryo 7405 ESR Table 3 3 Cryo target authorized personnel and contacts W B stands for the white board in Counting House CHAPTER 3 HALL SPECIFIC EQUIPMENT 17 3 6 Vacuum Systems The Hall A vacuum system consists of 5 separate but interconnected subsystems The largest is designed to supply the Hall A HRS see Chapter 3 7 with a self contained 5 x 1078 Torr vacuum that enables both spectrometers to be pumped down from atmospheric pressure in a few hours The target vacuum system is designed to maintain 1 x 1076 Torr in order to minimize contamination and provide an insulating vacuum for the cryo target Rough insulating vacuum for the 4 superconducting magnets is provided by a 360 cfm Roots type blower that can be connected to each magnet The beam line vacuum is maintained by 1 s ion pump system used in the accelerator ring and a small turbo pump located near the target The final subsystem is a differential pumping station located near the target exit port 3 6 1 Hazards Hazards associated with the vacuum system are due to rapid decompression in case of a window failure Loud noise can cause
5. EpicsDocumentation WWWPages EpicsDoc html JLab EH amp S Manual URL http www jlab org ehs ehsmanual JLab Personnel Safety System PSS manual URL http www jlab org accel ssg user_info html Accelerator Operations Directive URL http opsntsrv acc jlab org ops_docs online_document_files ACC_online_files accel_ops_directives pdf URL is available inside JLab site Jefferson Lab 12000 Jefferson avenue Newport News VA 23606 URL http www jlab org Telephone numbers 757 269 XXXX Pager numbers 757 584 XXXX Hall A Collaboration Hall A OSP full document info level 4 2013 URL http nallaweb jlab org github halla osp version osp level4 pdf edited by D Higinbotham 25
6. has been performed This calculation was performed as part of Code and JLab policy requirements and was reviewed by an independent JLab Design Authority This calculation TGT CALC 301 010 has been filed in the Hall A Cryotarget pressure system directory PS TGT XX 026 In summary this calculation conservatively indicates that the relief path and safety de vices limit the maximum developed pressure in the cell to less than the 120 psi for all credible overpressure conditions as required by ASME B31 3 322 6 3 Target Freezing Solid hydrogen is more dense than the liquid phase so freezing does not endanger the mechanical integrity of a closed system The chief hazard is that relief routes out of the system will become clogged with hydrogen ice making the behavior of CHAPTER 3 HALL SPECIFIC EQUIPMENT 15 the system during a warm up unpredictable For this reason the relief route bypasses the heat exchanger and should not freeze during any credible scenario In the unlikely event that the target temperature drops too low an alarm will sound and the target operator shall turn down the corresponding J T valve s or apply auxiliary heater power Target temperature can fall after IOC reboot After the reboot the high power heater will be reset to zero before going back to PID control Although the time the high power heater is zero is short for about 1 minute the temperature will drop To prevent this from happening an auxiliary heater is used in
7. have a great deal of stored energy as they are large inductors Always make sure people are clear of them and that the dump resistor is attached to the magnet Under no circumstances should any panel of any magnet power supply be opened by someone other than authorized personnel due to the shock hazard This hazard is mitigated by signs and protective panels There are also signs posted listing the dangers of high magnetic fields 3 7 3 Responsible Personnel In the event that problems arise during operation of the magnets qualified personnel should be notified see Table 3 5 This includes any prolonged or serious problem with the source of magnet cryogens the ESR On weekends and after hours there will be a designated individual on call for magnet services Any member of the Hall A technical staff is qualified to deal with unusual magnet situations but in the event of serious problems the technician on call should be contacted CHAPTER 3 HALL SPECIFIC EQUIPMENT 19 Name first last Dept Call 5 e mail Comment Tel Pager Tech on Call Hall A W B Contact Ed Folts Hall A 7857 Web foltsQjlab org Jack Segal Hall A 7242 segal jlab org Heidi Fansler Hall A 6915 Web fansler jlab org Jessie Butler Hall A 5544 jbutler jlab org Andrew Lumanog Hall A 7459 327 5523 andrewlQjlab org Jason Glorioso Hall A 6258 831 8713 gloriosoQjlab org Mahlon Long Hall A 6436 770 5562 mlongQjlab org
8. hearing loss 3 6 2 Mitigations To mitigate the hazard all personnel in the vicinity of the large chamber with a window are required to wear ear protection when the chamber is under vacuum Warning signs must be posted at the area The scattering chamber is equipped with a large 0 016 thick aluminum window that allows the spectrometers to swing from 12 5 to 165 on the left side and 12 5 to 140 on the right side In order to protect this window when the Hall is open lexan window guards are installed At the inlet of the sieve slit a 8 diameter 7 mil kapton window is provided to separate the target chamber from the spectrometers Finally under the HRS detectors a 4 mil titanium window is provided Additionally all vacuum vessels and piping are designed as pressure vessels 3 6 3 Responsible Personnel The authorized personnel is shown in Table 3 4 Name first last Dept Call 5 e mail Comment Tel Pager Tech on Call Hall A W B Contact Ed Folts Hall A 7857 Web folts jlab org Table 3 4 Vacuum in Hall A authorized personnel W B stands for the white board in the counting house CHAPTER 3 HALL SPECIFIC EQUIPMENT 18 3 7 High Resolution Spectrometers The Hall A spectrometers are designed to perform high resolution and high accuracy nuclear physics experiments An absolute cross section accuracy of up to 1 is re quired by the physics program planned in the Hall
9. use are along the outside of the Gas Shed in a fenced area There are racks next to the Gas Shed for storage of full gas cylinders On the other side of the truck ramp there are racks for storage of both full and empty cylinders Hall A currently uses ethane argon ethanol carbon dioxide methane and nitrogen 3 10 1 Hazards Some of the gases that are used are flammable Also the gas bottles are under high pressure and can become missiles 3 10 2 Mitigations The bottles are located in a gas shed with the bottles secured so that they can not fall In Counting Room A there are two alarm panels associated with the gas systems for the detectors They are located on the far left end of the control console mounted one above the other The upper panel is a Gas Master flammable gas monitoring system The lower panel is a gas systems status indicator The Gas Master system will go into alarm if elevated levels of flammable gas are present in either of the Detector Shielding Huts or the Gas Shed The gas systems status will alarm if any of a number of faults are detected in the Hall A Wire chamber Gas System The LED for the specific fault will turn red to indicate which fault caused the alarm Response to an alarm should be to contact the personnel listed below 3 10 3 Responsible Personnel Maintenance of the gas systems is routinely performed by the Hall A technical staff Shift personnel are not expected to be responsible for maintaining the d
10. 33 or Home 772 6098 Radiation damage to materials and electronics is mainly determined by the neu tron dose photon dose typically causes parity errors and it is easier to shield against Commercial off the shelf COTS electronics is typically robust up to neutron doses of about 10 3n cm If the experimental equipment dose as calculated in the RSAD is be yond this damage threshold the experiment needs to add an appendix on Evaluation of potential radiation damage in the experiment specific ESAD There the radiation dam age dose potential impact to equipment located in areas above this damage threshold as well as mitigating measures taken should be described 2 2 Fire The experimental halls contain numerous combustible materials and flammable gases In addition they contain potential ignition sources such as electrical wiring and equip ment General fire hazards and procedures for dealing with these are covered by JLab emergency management procedures The JLab fire protection manager Dave Kausch can be contacted at 269 7674 CHAPTER 2 GENERAL HAZARDS 5 2 3 Electrical Systems Hazards associated with electrical systems are the most common risk in the experimental halls Almost every sub system requires AC and or DC power Due to the high current and or high voltage requirements of many of these sub systems they and their power supplies are potentially lethal electrical sources In the case of superconducting magnets the sto
11. ab hazardous materials specialist Jennifer Williams can be contacted at 269 7882 2 9 Lasers High power lasers are often used in the experimental areas for various purposes Improp erly used lasers are potentially dangerous Exposure to laser beams at sufficient power levels may cause thermal and photochemical injury to the eye including retina burn and blindness Skin exposure to laser beams may induce pigmentation accelerated aging or severe skin burn Laser beams may also ignite combustible materials creating a fire hazard At JLab lasers with power higher than 5 mW Class IIIB can only be operated CHAPTER 2 GENERAL HAZARDS 7 in a controlled environment with proper eye protection and engineering controls designed and approved for the specific laser system Each specific laser systems shall be operated under the supervision of a Laser System Supervisor LSS following the Laser Operat ing Safety Procedure LOSP for that system approved by the Laboratory Laser Safety Officer LSO The LSO Bert Manzlak can be reached at 269 7556 Chapter 3 Hall Specific Equipment 3 1 Overview The following Hall A subsystems are considered part of the experimental endstation base equipment Many of these subsystems impose similar hazards such as those induced by magnets and magnet power supplies high voltage systems and cryogenic systems Note that a specific sub system may have many different hazards associated with it For each major syste
12. ard condition Cardiac pacemakers or other electronic medical devices may no longer functioning properly in the presence of magnetic fields Metallic medical implants non electronic being adversely affected by magnetic fields Lose of information from magnetic data storage driver such as tapes disks credit cards may also occur Contact Jennifer Williams at 269 7882 in case of questions or concerns 2 6 Cryogenic Fluids and Oxygen Deficiency Hazard Cryogenic fluids and gasses are commonly used in the experimental halls at JLab When released in an uncontrolled manner these can result in explosion fire cryogenic burns and the displacement of air resulting in an oxygen deficiency hazard ODH condition The hazard level and associated mitigation are dependent on the sub subsystem and cryogenic CHAPTER 2 GENERAL HAZARDS 6 fluid However they are mostly associated with cryogenic superconducting magnets and cryogenic target systems Flammable cryogenic gases used in the experimental halls include hydrogen and deuterium which are colorless odorless gases and hence not easily detected by human senses Hydrogen air mixtures are flammable over a large range of relative concentrations from 4 to 75 H2 by volume Non flammable cryogenic gasses typically used include He and nitrogen Contact Henry Robertson at 269 7285 or Mathew Wright at 269 7722 in case of questions or concerns 2 7 Vacuum and Pressure Vessels Vacuum and or pressure vessels ar
13. e CEBAF accelerator and the experimental hall All work on the beamline must be coordinated with both physics division and accelerator division in order to ensure safe and reliable transport of the electron beam to the dump 3 3 1 Hazards Along the beamline these various hazards can be found These include radiation areas vacuum windows high voltage and magnetic fields 3 3 2 Mitigations All magnets dipoles quadrupoles sextupoles beam correctors and beam diagnostic devices BPMs scanners Beam Loss Monitor viewers necessary for the transport of the beam are controlled by Machine Control Center MCC through EPICS 1 except for special elements which are addressed in the subsequent sections The detailed safety operational procedures for the Hall A beamline should be essentially the same as the one for the CEBAF machine and beamline Personnel who need to work near or around the beamline should keep in mind the po tential hazards e Radiation Hot Spots marked by ARM or RadCon personnel e Vacuum in the beam line tubes and other vessels e Thin windowed vacuum enclosures e g the scattering chamber Electric power hazards in vicinity of the magnets Magnetic field hazards in vicinity of the magnets and e Conventional hazards fall hazard crane hazard etc These hazards are noted by signs and the most hazardous areas along the beamline are roped off to restrict access when operational In particular the sca
14. e commonly used in the experimental halls Many of these have thin Aluminum or kevlar mylar windows that are close to the entrance and or exit of the vessels or beam pipes These windows burst if punctured accidentally or can fail if significant over pressure were to exist Injury is possible if a failure were to occur near an individual All work on vacuum windows in the experimental halls must occur under the supervision of appropriately trained JLab personnel Specifically the scattering chamber and beam line exit windows must always be leak checked before service Contact Will Oren 269 7344 for vacuum and pressure vessels issues 2 8 Hazardous Materials Hazardous materials in the form of solids liquids and gases that may harm people or property exist in the JLab experimental halls The most common of these materials include lead beryllium compounds and various toxic and corrosive chemicals Material Safety Data Sheets MSDS for hazardous materials in use in the Hall is available from the Hall safety warden These are being replaced by the new standard Safety Data Sheets SDS as they become available in compliance with the new OSHA standards Handling of these materials must follow the guidelines of the EH amp S manual Machining of lead or beryllia that are highly toxic in powdered form requires prior approval of the EH amp S staff Lead Worker training is required in order to handle lead in the Hall In case of questions or concerns the JL
15. ed to these Codes however all alterations of the system are in compliance Fur ther the relief system has been modified to meet these Code requirements All currently used cells and cell blocks also meet the requirements of the B31 3 Code The large volume storage tanks located outside the Hall also meet the requirements of the ASME Boiler and Pressure Code and bear an ASME nameplate These tanks are inspected on a regu CHAPTER 3 HALL SPECIFIC EQUIPMENT 14 lar basis and currently or will by time of operation meet the National Board Inspection Code requirements Target Cells The target cells themselves represent the most likely failure point in the hydrogen system The outer wall is made of 0 006 in thick aluminum The entrance and exit windows are thinner but no less than 0 004 in There is one 15 cm long cell bolted on to each cell block The cell has an outer diameter of 3 inches The upstream windows are connected to 0 8 in diameter tubes with flanges which are also bolted on to the cell block A vertical flow diverter plays a role to make the coolant flow in vertical direction to help remove the beam heating more effectively The cell and cell block components have been pressure tested hydro statically to meet the requirements of the ASME B31 3 2008 Process Piping Code The design pressure of the current cell is 100 psi Pressure Relief The gas handling and controls systems have been designed to prevent excessive pressure build up in the s
16. erformed by the technical staff prior to closing the Hall and a remote camera allows shift worker to inspect the area e Any motion that takes a spectrometer inside 14 degrees or outside X degrees X being specified in the pre run checklist and noted on the whiteboard during a run must be supervised by a trained Hall A technician 3 8 3 Responsible Personnel Following the experimental run plan as posted in the counting house by the run coordi nator shift workers are allowed to rotate the HRS following guidelines of the standard equipment manual In the event of a problem getting the spectrometers to rotate the run coordinator should notified If the run coordinator is unable to solve the problem and with the run coordinators concernence qualified personnel should be notified to repair the problem see Table 3 6 On weekends and after hours please only use the tech on call number It should be noted that for experiments that are using thick targets at high current it is not uncommon that the produced radiation will cause the motion system to require a hard reset Name first last Dept Call 5 e mail Comment Tel Pager Tech on Call Hall A W B Contact Ed Folts Hall A 7857 Web foltsQjlab org Jack Segal Hall A 7242 segal jlab org Heidi Fansler Hall A 6915 Web fansler jlab org Jessie Butler Hall A 5544 jbutler jlab org Andrew Lumanog Hall A 7459 327 5523 andrewlQjlab org Jason Glorioso Ha
17. etector gas systems see Table 3 8 for the names of persons to be contacted in case of problems Name first last Dept Call 5 e mail Comment Tel Pager Tech on Call Hall A W B Contact Jack Segal Hall A 7242 segal jlab org Table 3 8 Responsible personnel for detector gas system CHAPTER 3 HALL SPECIFIC EQUIPMENT 23 3 11 Drift Chambers The High Resolution Spectrometer Vertical Drift Chambers provide a precise 125 um measurement of the position and angle of incidence of both recoil electrons in the HRSe and knockout protons in the HRSh at the respective spectrometer focal planes This information may be combined with the knowledge of the spectrometer optics to determine the position and angle of the particles in the target Operation of the Hall A drift chambers requires the application of both High Voltage HV across the chambers themselves and Low Voltage LV across the preamp disc cards which are mounted on the sides of the VDCs within the confines of the protective aluminum Faraday cage The chamber gas is a combination of argon Ar and flammable ethane C2H which is bubbled through alcohol Gas is routed from bottles located in the Hall A gas supply shed to gas supply control panels located on the main level of the space frames in the detector huts 3 11 1 Hazards The following hazards are associated with the chambers The High Voltage System The Bertan 377N HV low current p
18. ewed by an independent expert are used to perform this task This task shall only be performed by system experts There are three flammable gas detectors installed one on top of the target one each on top of the hydrogen and deuterium gas panels to provide early detection of hydro gen deuterium leaks These detectors are sensitive and calibrated over the range from 0 to 50 Lower Explosive Limit LEL of hydrogen The electro chemical sensors were manufactured by Crowcon Detection Instruments LTD and the readout four channels was purchased from CEA Instruments Inc The Gas Master Four System The readout unit provides two alarm levels per channel The low level alarm is tripped at 20 of LEL while 40 of LEL activates the high level alarm Each channel has a relay output for both low and high level alarm states and there is also a set of common relays for both alarm levels these common relays respond to the logic of the sensor inputs Gas Handling System The most important aspect of hydrogen safety is to minimize the possibility of explosive mixtures of hydrogen and oxygen occurring Therefore the gas handling system has been made of stainless steel components wherever possible and as many junctions as possible have been welded Flanged connections are made with metal seals where possible Reasonable measures have been implemented to ensure that the system pressure does not fall near or below atmospheric pressure The pressure in the ga
19. livered by the Hall A gas system described elsewhere The Cherenkov does have pho tomultiplier tubes and thus high voltage 3 12 1 Hazards This detector is operated under high voltage and makes use of a gas system 3 12 2 Mitigations The Cherenkov counter PMTs use high voltage Care is required when handling any components of the counter and the body of the Cherenkov counter must be grounded The maximum operating voltage on the PMTs is about 2 000 V but nominally they are operated around 1 000 V The voltage must be set to zero before the HV cable will be connected or disconnected from HV divider The HV cables must be disconnected from all HV dividers before the replacement of any PMT on the gas Cherenkov counter Gas is supplied by the Hall A gas handling system and thus the gas bottles are outside the experimental hall and far from the equipment The detector itself can not be over pressurized and the volume of gas is small 3 12 3 Responsible Personnel The individuals responsible for the operation of the gas Cherenkov counters are given in Table 3 10 Name first last Dept Call 5 e mail Comment Tel Pager Bogdan Wojtsekhowski Hall A 7191 bogdanwQjlab org Contact Jack Segal Hall A 7242 segal jlab org Table 3 10 Gas Cherenkov authorized personnel Bibliography 1 EPICS Documentation WWW page URL http www epics org see also http www aps anl gov asd controls epics
20. ll A 6258 831 8713 gloriosoQjlab org Mahlon Long Hall A 6436 770 5562 mlong jlab org Table 3 6 List of HRS responsible personnel where W B stands for the white board in the counting house 3 9 Scintillator and Shower Counters Many of the detector systems in Hall A make use of photomultiplier tubes These include scintillators shower detectors and aerogel Cherenkovs CHAPTER 3 HALL SPECIFIC EQUIPMENT 21 3 9 1 Hazards The personnel hazard with these devices is the high voltage This same hazard can damage the equipment if the voltage is left on when a tube is exposed to room lighting 3 9 2 Mitigations The bases on the phototubes are high voltage devices and the high voltage channel must be turned off and the SHV cable removed before handling The maximum negative voltage for both the PMTs and dynode chain is 3 kV In actual use however there should be no need to exceed the 1 8 2 1 kV operating parameters since both PMTs and dynode chain have high gain Nevertheless the bases are high voltage devices and care should be exercised during handling and setup The external aluminum parts the front and rear housing and the back plate 17 are all grounded via the ground of the BNC 18 and SHV 19 connectors Since the back plate is connected to the coupling nut via the three steel posts the front plate is also grounded via the coupling nut and the back plate Common sense however dictates that the base
21. m the hazards mitigations and responsible personnel are noted The material in this chapter is a subset of the material in the full Hall A operations manual and is only intended to familiarize people with the hazards and responsible per sonnel for these systems It in no way should be taken as sufficient information to use or operate this equipment 3 2 Checking Tie in To Machine Fast Shutdown Sys tem In order to make sure that hall equipment that should be tied into the machine fast shutdown FSD system has been properly checked the hall work coordinator must be notified by e mail prior to the end of each installation period by the system owner that the checks been performed in conjunction with accelerator i e checking that equip ment s signals will in fact cause an FSD These notifications will be noted in the work coordinator s final check list has having been done System owners are responsible for notifying the work coordinator that their system has an FSD tie in so it can be added to the check list 3 3 Beamline The control and measurement equipment along the Hall A beamline consists of various elements necessary to transport beam with the required specifications onto the reaction CHAPTER 3 HALL SPECIFIC EQUIPMENT 9 target and the dump and to simultaneously measure the properties of the beam relevant to the successful implementation of the physics program in Hall A The beamline in the Hall provides the interface between th
22. n ual and will start by describing general types of hazards that might be present in any of the JLab experimental halls This document then addresses the hazards associated with sub systems of the base equipment of the experimental hall and their mitigation Responsible personnel for each item is also noted In case of life threatening emergen cies call 911 and then notify the guard house at 5822 so that the guards can help the responders This document does not attempt to describe the function or operation of the various sub systems Such information can be found in the experimental hall specific Operating Manuals Chapter 2 General Hazards 2 1 Radiation CEBAF s high intensity and high energy electron beam is a potentially lethal direct ra diation source It can also create radioactive materials that are hazardous even after the beam has been turned off There are many redundant measures aimed at preventing accidental exposure of personnel to the beam or exposure to beam associated radiation sources that are in place at JLab The training and mitigation procedures are handled through the JLab Radiation Control Department RadCon The radiation safety de partment at JLab can be contacted as follows For routine support and surveys or for emergencies after hours call the RadCon Cell phone at 876 1743 For escalation of ef fort or for emergencies the RadCon manager Vashek Vylet can be reached as follows Office 269 7551 Cell 218 27
23. o a oe sacr de ee eg en kegu 17 3 7 High Resolution Spectrometers ooa a e eee ee ens 18 CONTENTS 2 3 8 3 9 3 10 3 11 3 12 ME AOS e a O ha ON E A A 18 a AVON ica rca rra ps Ho he ee eS 18 S00 Respansible Personnel os sps moce i ero a 18 Spectrometer Rotation lt a 2 5 6 22464 daa a a aR 19 E Hazarde a od ea da la e 19 Aa MNUNPAUO S s rr recia a AAA GO 19 3 9 9 Responsible Personnel e426 62 we oe dee aa Oe 20 scintillator and Shower Counters ses sertas er s4 4 lt lt 20 391 cee sa EA A 21 Gene Mitigation scos bch bee oe bea Boe Rw Oe a 21 3 9 3 Responsible Personnel lt 4 ociosas 21 Detector Gas Supply System 22 A II EN 22 310 2 NUNESUODS iia irradia e 22 3 10 3 Responsible Personnel eens 22 Drift Chambers o o oe ak eB ee r macs u rad ee Ee EE 23 SALI Hazarda s bani aa Ani ea oo ee Oa ee SP ee ek a a A 23 ALI MUNDOS sand ee ek 6 we ee m e OR A 23 3 11 3 Responsible Personnel oaoa eens 23 Gas Cherenkov Counters gt s sacok EA Bree a en 24 A AN 24 a NUNES ies E OE eo A E Se OR 24 3 12 3 Responsible Personnel 2 4 644 ea oc 2 lt 24 Chapter 1 Introduction The ESAD document describes identified hazards of an experiment and the measures taken to eliminate control or mitigate them This document is part of the CEBAF experiment review process as defined in Chapter 3120 of the Jefferson Lab EHS amp Q ma
24. of the eight dipoles that lead to Hall A and in turn determine the beam energy a ninth dipole wired in series with the rest is located in a special shed near the hall A counting house 3 4 1 Hazards The ninth dipole presents a magnetic field hazards as well as the mapper creating a mechanical hazard as it moves Very high currents are also present in the magnet 3 4 2 Mitigations The ARC energy system s dipole magnet and motion system is located in a locked shed with access limited to authorized persons which are listed in the standard equipment manual To be added to the list contact Douglas Higinbotham The standard operation mode of the integral measurement setup is the remote mode through the network from the counting house CHAPTER 3 HALL SPECIFIC EQUIPMENT 11 3 4 3 Responsible Personnel The arc requires both accelerator and physics personnel to maintain and operate It is very important that both groups stay in contact and that any work on the system be coordinated between the two groups Therefore this system has both a physics division and accelerator division point of contact Name first last Dept Call 5 e mail Comment Tel Pager Douglas Higinbotham Hall A 7851 doug jlab org Physics Con tact Rick Gonzales Hall A 7198 gonzalesQjlab org Accelerator Contact Table 3 2 Beamline physics division and accelerator division points of contact CHAPTER 3 HALL SPECIFIC EQUIPMENT 12
25. ower supply provides a nominal 4 00 kV Explosive Gas The Ar CjH chamber gas is explosive and must be handled accordingly Further gas flow should be maintained for at least 24 hours prior to the enabling of HV High Pressure Gas Bottles The gas used in the chambers is supplied in high pressure gt 2000 psi gas bottles This confined high pressure gas represents a tremendous potentially lethal amount of stored energy 3 11 2 Mitigations For the HV red HV RG 59 U cable good to 5 kV with standard SHV connectors is used to connect the power supply to a Hammond splitter box and then to connect the splitter box to each of the three high voltage planes in a given VDC A given chamber draws a current from 50 100 nA Thus when servicing the chambers the HV for that element must be turned off and disconnected The high pressure gas bottles are stored far from the equipment in a controlled area as discussed in the Hall A gas handling section 3 11 3 Responsible Personnel The individuals responsible for the operation of the VDC are shown in Table 3 9 CHAPTER 3 HALL SPECIFIC EQUIPMENT 24 Name first last Dept Call 5 e mail Comment Tel Pager Jack Segal Hall A 7242 segal jlab org Contact Bogdan Wojtsekhowski Hall A 7191 bogdanw jlab org Table 3 9 VDC responsible personnel 3 12 Gas Cherenkov Counters The Hall A gas Cherenkov detectors are filled with CO at atmospheric pressure as de
26. parallel to the regular heater During an IOC reboot the auxiliary heater supply will replace the main supply to keep the temperature from dropping unacceptably Since 2008 the IOC has been relocated to the entry labyrinth where the radiation exposure has been minimized As a result the frequency of IOC reboots has dramatically decreased ODH The total volume of the targets is relatively small with the entire scattering chamber containing only 9 000 STP of target gas when all three targets are full As the scattering chamber is located in the middle of Hall A i e not in a confined area and the total Hall A volume is 40 000 m3 the ODH hazard is minimal Further Reading More detailed information about the mitigations discussed above can can be found in the full Hall A operations manual 6 3 5 3 Responsible Personnel The principle contacts for the cryogenic targets are listed in table 3 3 Every shift must have a trained target operator whenever the cryogenic targets contain liquid These operators are trained by one of the experts listed in the table and certified by J P Chen Silviu Covrig or Greg Smith CHAPTER 3 HALL SPECIFIC EQUIPMENT 16 Name first last Dept Call 5 e mail Comment Tel Pager Hall A Technicians Tech on Call Hall A W B Vacuum Ed Folts Hall A 7857 Web folts jlab org Vacuum Hall A Physicists Cryotarg on Call Hall A W B Cryotarget Jian Ping Chen Hall
27. red energy is so large that an uncontrolled electrical discharge can be lethal for a period of time even after the actual power source has been turned off Anyone working on electrical power in the experimental Halls must comply with Chapter 6200 of the Jefferson Lab EHS amp Q manual and must obtain approval of one of the responsible personnel The JLab electrical safety point of contact Todd Kujawa can be reached at 269 7006 2 4 Mechanical Systems There exist a variety of mechanical hazards in all experimental halls at JLab Numerous electro mechanical sub systems are massive enough to produce potential fall and or crush hazards In addition heavy objects are routinely moved around within the experimental halls during reconfigurations for specific experiments Use of ladders and scaffold must comply with Chapter 6231 of the Jefferson Lab EHS amp Q manual Use of cranes hoists lifts etc must comply with Chapter 6141 of the Jefferson Lab EHS amp Q manual Use of personal protective equipment to mitigate mechanical hazards such as hard hats safety harnesses and safety shoes are mandatory when deemed necessary The JLab technical point of contact Suresh Chandra can be contacted at 269 7248 2 5 Strong Magnetic Fields Powerful magnets exist in all JLab experimental halls Metal objects being attracted by the magnet fringe field and becoming airborne possibly injuring body parts or striking fragile components resulting in a cascading haz
28. s are not to be handled while under high voltage even when multiple grounding connections are provided The mu metal shield is also under high voltage since it is connected to the cathode Electrical isolation between the mu metal shield and the front tubular housing is assured by the high dielectric retainer ring 12 and the plastic insulator 09 at the free end of the mu metal shield The air gap between the mu metal shield and the front tubular housing is 6 mm thus the breakdown value 18 kV far exceeds the maximum 3 0 kV of the PMT In the event that the mu metal shield is inserted without the plastic insulator ring or someone decides to operate the base without the outside housings the 11 MQ resistors between the HV and the mu metal shield will restrict the current flow through the mu metal shield and the person s hands to less than 0 2 mA with 2 1 kV on the base 3 9 3 Responsible Personnel The individuals responsible for the operation of the trigger counters are shown in Table wie Name first last Dept Call 5 e mail Comment Tel Pager Bogdan Wojtsekhowski Hall A 7191 bogdanw jlab org Contact Jack Segal Hall A 7242 segal jlab org Table 3 7 Trigger counters responsible personnel CHAPTER 3 HALL SPECIFIC EQUIPMENT 22 3 10 Detector Gas Supply System The Hall A detector gas systems are located in the Hall A Gas Shed alongside of the truck ramp for Hall A The gas cylinders in
29. s handling system is monitored in numerous places Most importantly the absolute pressure of the target is viewed by two pressure transducers one on the fill line PT127 for Hz and PT136 for Da and one on the return line PT131 for H and PT140 for D These pressures are also measured by manual gauges The fill line gauges are PI126 for Hz and PI135 for D The return line gauges are designated PI130 H and PI139 D The gas tanks are viewed with both pressure transducers PT133 for hydrogen and PT142 for deuterium and pressure gauges P1123 for hydrogen and PI112 for deuterium If the pressures significantly deviate either from one another or from the normal operating pressure the target operator shall call the target expert on call When they differ from one another it often is due to a failure of one or more of the pressure transducers If more than one deviate significantly from the normal operating pressure it could be due to temperature change or could be a more serious situation i e a leak in the system The target system is considered by JLab to be a Pressure System Thus the design and construction of the system must meet the requirements of the the most applicable ASME pressure code The Codes of Record for the system are ASME Boiler and Pres sure Vessel Code Section VIII Division 1 and ASME B31 3 Process Piping Code These Codes have conservative safety allowances The system was not originally designed or construct
30. the beam goes from on to off or from off to on since the temperature change is out of normal range The ALH can also repeatedly alarm if there are noisy analog channels If the AH alarms repeatedly or the cause of the alarm is not clear the target operator should contact the on call target expert When full power beam with tiny beam spot hit the cryotarget there is a danger that the beam can melt the target cell The fast raster is used to prevent this from happening Every time when moving the cryotarget into beam position the target operator must check to make sure that the faster raster is on and has a reasonable size for beam current above 5 uA 3 5 1 Hazards The cryogenic hydrogen and deuterium targets present a number of potential hazards such as the fire explosion hazard of the flammable gas as well as the hazards connected with the vacuum vessel and the of handling cryogenic liquids ODH and high pressure 3 5 2 Mitigations Flammable Gas The basic idea behind safe handling of any flammable or explosive gas is to eliminate oxygen required for burning and to prevent exposure to any energy source that could cause ignition In the Hall A environment the most likely source of oxygen is of course the atmosphere and the most likely ignition sources are from electrical equipment Oxygen is removed from the internal volumes of the system by pumping and CHAPTER 3 HALL SPECIFIC EQUIPMENT 13 purging the system Extensive procedures revi
31. ttering chamber with it s large volume and thin windows requires hearing protection once it has been evacuated Signs are posted by RadCon for any hot spots along the beamline and RadCon must be notified before work is done in a posted area Some magnets as the Moller spectrometer elements are covered with plastic sheets for electric safety Any access to these magnets requires the Lock and Tag procedure 2 and the appropriate training including the equipment specific one Additional safety information is available in the following documents CHAPTER 3 HALL SPECIFIC EQUIPMENT 10 EH amp S Manual 2 PSS Description Document 3 Accelerator Operations Directive 4 3 3 3 Responsible Personnel Since the beamline requires both accelerator and physics personnel to maintain and operate and it is very important that both groups stay in contact that any work on the Hall A beamline is coordinated Name first last Dept Call 5 e mail Comment Tel Pager Hall A Physicists Douglas Higinbotham Hall A 7851 doug jlab org 1st Contact Robert Michaels Hall A 7410 romQjlab org 2nd Contact Liaisons from Accelerator Division Hari Areti Accel 7187 aretiQ jlab org to Physics Yves Roblin Accel 7105 roblin jlab org to Hall A Table 3 1 Beamline physics division and accelerator division points of contact 3 4 Arc Energy Measurement In order to determine the integral field
32. which implies 107 accuracy in the determination of particle momenta and 0 1 mr in the knowledge of the scattering angle 3 7 1 Hazards The spectrometers have associated vacuum electrical cryogenic and magnet systems all of which can be extremely dangerous due to the size and stored energy in the systems Hazards of rotating the spectrometers as well as the particle detectors that get placed inside the detector hut of the spectrometer are covered in detail in following sections 3 7 2 Mitigations The vacuum systems associated with the spectrometers are essentially pressure vessels and care should be exercised so as not to puncture the windows During hall maintenance covers are placed over the windows to help mitigate accidentally hitting a window The magnets themselves are installed inside cryostats These vessels are exposed to high pressures and are therefore equipped with safety relief valves and burst discs The hydraulic system originally intended to operate the vertical positioning system VPS and the horizontal positioning system HPS has been dismantled after problems were encountered during the initial attempted operation of the system so this is no longer a hazard The cryogenic system operates at an elevated pressure at 4K One must guard against cold burns and take the normal precautions with pressure vessels when operating this system Only authorized personnel are permitted to install and take out U tubes The magnets
33. ystem in order to protect the target cells from rupture It has been determined that the worst case pressure load will arise from an insulating vacuum loss The calculation of this load was reviewed by a JLab Design Authority not associated with the target group The estimated relief load is 350 scfm of hydrogen The primary relief path is 2 inch Sch 10s pipe connected to the recovery tank There is a separate relief valve on the fill side of the target CRV30 for Hz and CRV59 for Da This valve is not capable of handling the entire relief load from an insulating vacuum loss event so overpressure protection of the system on each loop is provided by an ASME relief valve which meets the requirements of the Code The capacity of this relief is 1100 scfm for hydrogen The relief valves exhaust to the Hall A hydrogen vent line This line is 2 inch Sch 10s IPS stainless steel pipe 150 ft long The vent line is continuously purged with 1 psig of He gas from the House Helium supply The scattering chamber and pump purge vacuum pumps are also exhausted to this line Thus any vented target gas is placed in an inert environment until it is released outside of Hall A Additionally each gas tank has one relief valve as required by Code Scattering Chamber Vacuum The scattering chamber will be leak checked before service but the possibility of vacuum loss cannot be eliminated A conservative calcu lation estimating the relief load on the relief system of each loop
Download Pdf Manuals
Related Search