All Staff Memos
|Date:||October 20, 1999|
|From:||Larry Cardman and Andrew Hutton for the Nuclear Physics
Experiment Scheduling Committee
|Subject:||Accelerator Schedule: January 2000 - December 2000|
Attached is the accelerator operations schedule for the period through December 2000. The overall operations has been constrained to a level of 31 weeks/year as a result of the laboratory’s operating budget level for FY2000. This is up slightly from last year’s 30.5 week operation as a result of the changes in the maintenance/development cycle outlined below.
The Jefferson Lab Nuclear Physics Experiment Scheduling Committee developed the schedule. Committee members are: Larry Cardman and Andrew Hutton (Co-Chairmen), Hari Areti, Roger Carlini, Bernhard Mecking, Kees de Jager, Claus Rode, Mike Seeley, Charlie Sinclair, and Will Oren. Nathan Isgur provided advice. As has been the norm, a number of meetings of this committee were necessary to resolve conflicting requirements and to ensure that sufficient resources would be available at the laboratory to properly stage and carry out each of the experiments. The schedule was derived by looking at the requests for major installation work in the experimental halls, evaluating the number and kinds of people needed, and then scheduling to minimize overlap. The schedule request forms again proved quite useful in identifying the detailed requirements of each experiment. Information on other laboratory engineering priorities was included to ensure that the required preparatory work could be completed in time. This provided a rough overview of when each hall would be down.
Each hall leader took the requests for running time submitted by the experiment spokespersons and prioritized them based on the PAC recommendations and other considerations as outlined in the scheduling committee charter. Scheduled time for Halls B and C was again calculated using an estimated overall efficiency of simultaneous hall and accelerator operation of 50%; this value is consistent with last year's experience for these halls. Scheduled time for Hall A was calculated using an estimated overall efficiency of 60%; this was consistent with recent experience and should permit us to complete more experiments in the hall this year. The final schedule was then reached by a series of compromises in running order within each experiment and between halls to work around incompatibilities.
This is the fifth schedule with substantial polarized beam operations. There are only two beam energies (2.115 and 4.230 GeV) at which purely longitudinal spin can be delivered simultaneously to all three halls when the halls have the same energy. There are, however, many combinations of passes and linac energies at which it is possible to deliver beams with precisely longitudinal polarization to two halls simultaneously, and many combinations at which it is possible to deliver nearly longitudinal polarization to three halls. (See the note at the end of this memo for further information.) Experimenters scheduled for periods involving multiple-hall polarized beam delivery should consider the possible impact of a transverse polarization component on their measurements, and provide the laboratory with a maximum allowable transverse component if appropriate.
In an effort to optimize polarized beam running, we have scheduled many weeks of operation at "unusual" energies that are consistent with good polarization in multiple halls. The details vary from run period to run period and hall by hall. In the worst case, the effective polarization delivered to a hall will be reduced to about 86% of the nominal maximum available from the cathode. This reduction is due to the angle at which the polarization vector will be set relative to the beam direction in the hall in a compromise that will optimize delivery to all halls. In all cases we intend to set the Wien filter to a value that maximizes the sum of the squares of the polarization provided to all halls scheduled to receive polarized beam.
The standard section at the end of this memo on "the meaning of priority on the accelerator schedule" has again been revised slightly to clarify a few questions about this policy. All users with running experiments should read it carefully.
It is clear that we will continue to have a great deal less flexibility for changing energies in the different halls during polarized beam running. This is because there are many instances where the nominal linac energy and number of recirculations for the running halls provide reasonable polarization, but where changing the number of recirculations for one of the running halls results in nearly transverse polarization.
The schedule attached represents our best effort to optimize the physics output of the laboratory consistent with our resource constraints and the technical evolution of the accelerator and the experimental equipment. In the material that follows, we outline the technical considerations that influenced the scheduling, and outline the planned program.
This past year the accelerator has delivered high power beams to physics experiments (up to 750 kW was delivered for a period of weeks, split between Hall A and Hall C). In April, 5.5 GeV beam was delivered successfully to all three halls. The accelerator availability was as good at 5.5 GeV as it has been at lower energies, but the trip rate was considerably higher than at lower energies. This can be expected to improve with time but the asymptotic limit is difficult to estimate at the moment. The loss in availability due to trips (up to 8%) has been included in the evaluation of accelerator beam delivery, and efforts are underway to reduce the number of trips. In the January shutdown, the cryomodule that has been in the FEL will be transferred to CEBAF. This should drastically reduce the number of trips at 5.5 GeV and prepare the way for operation at 6 GeV later in the year.
There continue to be occasional problems with tails on the Hall B beam from the beams delivered to Halls A and/or C. Scrapers have been installed in the injector and have been commissioned, and halo monitors have been installed at the Lambertson magnet used to split the three beams to the halls. This continues to be a prime focus of attention.
The big success story this past year continues to be the polarized source. Since the last memo, most running has been from the strained gallium arsenide cathode, which has delivered polarization up to 75% and currents up to 50 µA delivered for months at a time to up to three halls simultaneously. The cathode lifetime is still too long to be estimated reliably; it is of order 10,000 μA-hours. We have demonstrated that we can deliver currents on this scale from high polarization photocathodes for long periods of time. Recent studies by the HAPPEX collaboration indicate that it is possible to run future parity experiments with the strained gallium arsenide cathode providing a consequent improvement in the accuracy of the asymmetry measurement. In the June shutdown, a second polarized gun was installed horizontally in the injector, and the old, vertical polarized gun was also modified and installed horizontally.
There were teething troubles with these two guns in July and again in September, and there were two short periods where beam was delivered from the thermionic gun. The problem is that the guns tend to arc during high voltage conditioning, and this poisons the cathodes. Several different mechanisms may contribute, and modifications are being carried out to address all of the suspected causes. However, a question mark remains over the availability of the polarized source until the origin of the problems is nailed down definitively.
Separate lasers for each hall are combined optically to provide independent control of the three beam intensities, and obtaining the desired spin orientation has been reasonably easy due to the availability of the fast Mott measurements in the injector. However, the detailed layout of the laser combining optics has been modified several times to minimize the cross-talk between halls. The constraints of obtaining the correct polarization orientation in two or three halls influence the scheduling process. Dealing with these problems may reduce the polarization available on experimental targets to as low as 0.8 times the polarization of the beam at the cathode; for the present schedule we have managed to limit the polarization loss to no more than 14%.
Starting in February 2000, we are trying a new cycle for the scheduled maintenance and machine development periods. We will now take a longer period every three weeks, starting at 8:00 AM on Monday morning and ending midnight on Thursday (a total of 11 shifts). In addition, on the weeks where no maintenance is being carried out, there will be a period of 4 hours on Tuesday morning devoted to recovering RF cavities, which we believe will help reduce the RF trip rate by maintaining the maximum number of cavities active, thus reducing the average gradient.
This cycle provides enough time to change out the cathodes and rebake the gun during the scheduled maintenance period when (and if) this is necessary. It also provides slightly more time for the gun during the scheduled maintenance period when (and if) this is necessary. The final effects of this new maintenance/development schedule are to provide slightly more time (~2½%) for beam to experiments and to reduce the frequency of beam recovery following a downtime, always a potential source of lost beamtime. Details are provided below in the section on Maintenance/Development.
Since the last schedule was released, Hall A completed a very successful second (and final) run of HAPPEX (E91-010, Souder/Finn), which studied the electroweak form factor of the proton with the goal of providing insight in to the strangeness distribution in the nucleon. HAPPEX was followed by the running of three photodisintegration experiments: E89-019 (Gilman/Holt/ Meziani), which measures proton polarization in the reaction; E99-007 (Gilman/Holt/Meziani), which measures deuteron photodisintegration at large angles; and E94-012 (Gilman/Holt), which measures photo-proton polarization in the reaction. These experiments are nearing completion as this schedule is released. We were able to complete the conditionally-scheduled four-day run of E89-028 (Finn/Ulmer), which measured polarization transfer in the reaction, providing a check on the assumptions of the Hall C experiment of Madey and Kowalski, which uses the same polarization transfer technique to determine GEn. E94-004 has been tentatively added to the schedule for October 19-25. It will be run if E89-019 and E94-012 are on track for meeting their scientific goals.
The firm portion of the Hall A schedule for the remainder of 1999 and the first half of 2000 begins with a four week shutdown to install the high power helium cryotarget that will be used to run E89-044 (Saha/Epstein/Mougey), an experiment to study 3He through electrodisintegration at high momentum transfer, and then E93-049 (van den Brand/Ent /Ulmer), an experiment to study polarization transfer in the 4He(e,e'p)3H reaction in the quasi-elastic scattering region. These two experiments are being mounted at this time to take advantage of the helium refrigerator capacity that is freed up by the installation (and subsequent running) of the HNSS experiment (E89-009, Tang) in Hall C. (We cannot run high-power helium targets in one hall simultaneously with high-power hydrogen targets in another due to refrigerator limitations.). Following the running of E93-049, the cryotarget will be restored to hydrogen operation and we will start E91-011 (Frullani/Kelly/Sarty), a high precision separation of the polarized structure functions in electroproduction of the Roper and delta resonances. This experiment will be completed in the first month and a half of the tentative portion of the schedule.
The tentative portion of the Hall A schedule includes: E97-111 (Templon), a systematic probe of short-range correlations via the reaction 4He(e,e'p) 3H; and E99-007 (Perdrisat), the extension of the GEp measurement to higher momentum transfer. The long shutdown between E97-111 and E99-007 is necessary to swap the detector packages between the two Hall A spectrometers so that the 'new' hadron spectrometer no longer has the maximum momentum operating limit now necessitated by the coil short in the present hadron spectrometer.
With this release of the schedule we announce our intent to install the new septa in Hall A early in 2001 (probably starting in March) and then run the first two experiments using them. To retain this tentative installation start, the collaboration behind these experiments and the septa must pass a formal readiness review before the September 2000 meeting of the scheduling committee (which would place the installation and execution of this experiment on the firm schedule). This review can be arranged through the hall leader, Kees de Jager, at the convenience of the collaboration, but it must take place no later than August 2000 if the collaboration wants to keep its place on the long-range schedule.
Hall B continues to interleave runs of the various "groups" that have been created for experiments with common running conditions. Since the last schedule release we completed the second major run on the e1 group (15 experiments on electron-induced reactions on a proton target). This was followed by the first portion of the e2 group of 8 experiments involving the first CLAS data-taking on multi-nucleon emission from nuclear targets. Next we had the second major run of the g6 group (experiments on vector meson production at high t and meson spectroscopy). Then we ran the first portion of the g2 group (4 experiments studying photon interactions with deuterium). We are currently running the g1 group of 7 experiments which involve photon-induced reactions on hydrogen targets.
The remainder of 1999 running in Hall B has been revised slightly to provide a better "fit" for the overall CLAS running schedule with the beam energies available in 2000. The g2 run now in progress will be followed by the g3 run group (3 experiments involving few-body targets). Year 2000 running begins with the e1 run group (originally scheduled for March 2000) followed by the e5 group (a measurement of the neutron magnetic form factor via precision measurements of the ratio of quasi-elastic electron-neutron to electron-proton scattering in deuterium) and then the "Rad Phi" experiment (E94-016, Rubin), which aims to measure rare radiative decays of the phi meson. The RadPhi experiment completed a test run this summer, and has prepared the submission on the results of that run that were a requirement for the readiness review that was to precede firm scheduling. However the readiness review could not be carried out before this schedule was released, so the experiment has been placed on the firm schedule, but with the caveat that it must pass the readiness review, which will be held in November, to retain its place on the schedule.
The tentative portion of the Hall B schedule begins with the completion of E94-016, which is followed by the installation (during the summer shutdown) of the polarized target for the eg1 run group. This target and run group are then tentatively scheduled to run for the remainder of 2000.
Since the last schedule was released, Hall C running has included: E96-003 (Holt), the extension of the earlier E89-012 photodisintegration experiment to higher energy; the completion of E91-007 (Milner), a study of the Q and A dependence of quasi-elastic scattering; E94-110 (Keppel), a measurement of the longitudinal and transverse contributions to the nucleon resonance region; and E97-006 (Sick), an investigation of the correlated spectral function and (e,e'p) reaction mechanism. The remainder of 1999 running will begin with the conversion of the Hall C cryotarget from hydrogen to helium operation (now in progress), and then running of the final portion of E91-016 (Zeidman), a study of the electroproduction of kaons and light hypernuclei. This will be followed by three days of development running for the G0 experiment, and then the installation of the installation of the hypernuclear spectrometer system (HNSS) in preparation for the execution of experiment E89-009 (Tang).
The firm portion of the Hall C 2000 schedule begins with the completion of the HNSS installation and its commissioning and running. E89-009 will be the third major installation experiment in Hall C, and it is expected to be completed by mid-May, at which time we will tear down the HNSS installation and reconfigure the hall for E93-038 (Madey, Kowalski), a measurement of the neutron electric form factor and the fourth major installation experiment in Hall C. E93-038 will not be completed until early 2001.
With this release of the schedule we once again indicate our intention to reinstall the UVa/Basel polarized target in Hall C either immediately following or shortly after the running of E93-038 (we may insert a short, single-arm experiment in between E93-038 and E93-026 if it provides a better overall fit to the running schedule). The E93-026 and E93-038 collaborations have identified a set of kinematic running conditions which will permit the same neutron detector blockhouse to be used for both experiments, and by running E93-026 immediately after E93-038 we will save the time that would otherwise be used for teardown and reconstruction of the neutron detector blockhouse. The blockhouse cannot be left on the floor during most other planned Hall C experiments because it interferes with the rotation of the SOS spectrometer. Current estimates of the schedule for the running of E93-038 would place the beginning of the polarized target re-installation in March 2001. In order for E93-026 to be placed on the tentative schedule for the first half of 2001, the collaboration must pass the first of their two formal readiness reviews before March 2000. This review will include an evaluation of the quality of the data obtained during the first run of this experiment last year.
Information about the Schedule
The accompanying revised schedule is fixed for the nine-month period September 1999 – June 2000, and tentative for the following six months. Because of the complex couplings between the hall operations during polarized beam running, all halls must continue to run in "calendar-driven" mode. The firm schedule for the second half of 2000 (and the tentative schedule for the first half of 2001) will be released late March or early April, following the meetings of the next cycle of the scheduling committee.
Footnotes to the Schedule
We summarize here the detailed footnotes to the schedule. They appear in the rightmost column of the schedule listing, and are listed at the earliest date in the schedule when they are applicable; many extend for a considerable time after they first appear. The first five footnotes apply to the entire schedule. All of the footnotes are repeated here for clarity and information.
- When two or three halls are scheduled, the relative priority listed in the schedule (in the order listed from left to right) is the relative priority of the halls. For example, A/B/C means that Hall A is the highest priority, Hall B has second priority, and Hall C has the lowest priority. If one of the halls has an asterisk, it means that its priority is conditional, and the conditions are given in appropriate footnotes at the beginning of the running of the affected experiment. If the conditions are not met, then the remaining two halls will have priority in the order listed.
- Energies listed in the schedule for the halls receiving polarized beam are the actual, delivered energies; they include the energy of the injector.
- In the "Accelerator" column, a "low" under Pol(arization) indicates planned use of either a bulk or a thin (but unstrained) GaAs cathode, implying that medium (~40%) polarization can be expected. A "high" under Pol(arization) indicates planned use of a strained GaAs cathode, implying high (~75%) polarization can be anticipated.
- When polarized beam is delivered to all three halls, it is not, in general, possible to provide pure longitudinal polarization to all users. We have optimized the beam energies to provide the highest longitudinal polarization (generally over 90%) to all halls during periods of scheduled two- and three-hall operation with polarization. In all cases, the orientation of the polarization at the injector will be optimized to maximize the sum of the squares of the polarization delivered to all halls using polarized beam.
- When polarized beam is provided at a new energy, the first shift of polarized beam operation should be used to verify polarization in the halls. Unfortunately, many users have tended to skip this step in the interests of more running time, thereby risking taking data for significant periods with incorrect polarization.
- E94-004 will be run here as scheduled only if E89-013 and E94-012 have met their scientific goals for the running period thru 8/22; if not, this period will be used by those two experiments as needed.
- The maximum beam current available to all three Hall A experiments that are scheduled using high power helium cryotarget experiments in Hall A may be limited by available refrigeration power; it will have to be determined empirically at the startup of the experiment. Note also that E91-016 has a "hard" end date due to the refrigerator constraints, which do not allow us to support simultaneous operation of both high power helium and high power hydrogen cryotargets.
- The maintenance period originally scheduled to begin 12/14 has been shortened to one day to permit additional running. Halls A and B will continue with their scheduled experiments for the two additional days. For the period from 12/8 thru 12/15, Hall C will be running background tests for the upcoming G0 experiment and (possibly) some single-arm data-taking if run conditions can be found that are compatible with the cryogenic load and switch-over demands associated with the E89-044 startup and running.
- For the week beginning December 17 we will attempt to operate the accelerator at a very low energy gain (250 MeV/linac or 500 MeV/pass) in order to be able to provide 2 GeV beam to E89-044 and simultaneously continue to provide 1.6 GeV beam for the g3 run group. In the event that operation at this low setting cannot be achieved within 24 hours of the start of the effort, we will restore the accelerator to "standard" energy settings and be forced to compromise the run conditions for one of the two halls.
- The value of 0.6 listed for the linac energy is to be taken as a three-digit accuracy number for this run period - the maximum acceptable energy for Hall A during this period is 1.245 GeV.
- On 5/15 and 6/5 we will carry out tests of the capability of the various accelerator system components to support a final energy of 6.0 GeV in preparation for future running at that energy. A major effort to refine high energy running will be the focus of the summer 2000 shutdown.
- The scheduling of E94-016 (the RadPhi experiment) for this period is conditional on the experiment passing its final readiness review, as outlined in the Hall B comments of this memo.
- The beginning of the installation effort for the Madey/Kowalski GEn experiment (E93-038) will be overlapped to the maximum extent possible with the removal of the HNSS. The E93-038 collaboration should develop an overall plan in consultation with Hall C management and engineering that minimizes the total down time etween the end of data-taking for the HNSS experiment and the beginning of commissioning for E93-038.
- For the first week of the summer 2000 down we will be carrying out tests to determine the maximum reliable operational energy for the accelerator. For Saturday and Sunday, August 5 and 6, Hall A will be closed to provide a beam dump for high beam power tests at high energy.
- For E93-038 running, which begins with commissioning efforts on September 8, we will promise to deliver the 30mA and try to deliver as much as 50mA from the strained cathode. This will, of course, depend on both the capability of the polarized source and the ability of the experiment to run with the higher luminosity. If this is possible, we will "split the difference" with the collabor ation on the P2Q associated with the higher luminosity. They will receive half the advantage in the form of higher net charge than originally scheduled, but the other half will be used to reduce the total days of beamtime for the experiment, permitting us to begin the changeover to the next experiment sooner and increase the experiment throughput in Hall C.
- On October 5, 2000 the APS/DNP meeting will be held in Williamsburg. As part of that meeting there will be a general tour of the experimental facilities at Jefferson Lab. We anticipate that roughly a shift of beam operations will be lost on this day to permit the tour to take place in an orderly and safe manner.
- For the run starting November 3, we will attempt to set up the linac for an energy gain of 1.143 GeV/pass, implying energies of 5.779 GeV for Halls A and B and an energy of 3.493 GeV for Hall C. This higher energy provides significantly better polarization to all three halls (worst case loss of polarization is 9%, rather than the 14% at the 1.115 GeV setting listed on the schedule). However, running at this higher energy will depend on the success of our energy upgrade efforts during the summer.
Additional General Information on Operations and Scheduling Constraints
The accompanying schedule is fixed for the nine-month period October 1998 - June 1999 and tentative for the following six months. Priorities have been assigned as "firm" for the period of the schedule that is fixed; the tentative priorities set for the June-December 1999 period will be reviewed in March, when the schedule for that period becomes fixed. As noted earlier in this memo, the operation of polarized beams in more than one hall puts severe constraints on our ability to change beam energies.
The Meaning of Priority on the Accelerator Schedule
Generally, the assignment of priority to a hall means that the identified hall will have the primary voice in decisions on beam quality and/or changes in operating conditions. We will do our best to deliver the beam conditions identified in the schedule for the priority hall. It will not, however, mean that the priority hall can demand changes in beam energy that would effect planned running in the other halls without the consent of the other halls. Of course, final authority for decisions about the unplanned changes in machine operation will rest with the laboratory management.
The operation of more than one hall at Jefferson Lab substantively complicates the interaction between the experimenters and the accelerator operations group. It is in the interests of the entire physics community that the laboratory be as productive as possible. Therefore, we require that the run coordinators for all operating halls do their best to respond flexibly to the needs of experiments running in other halls. The run coordinators for all experiments either receiving beam or scheduled to receive beam that day should meet with the Program Deputy at 7:45 AM in the MCC on weekdays, 8:30 AM on weekends.
To provide some guidance and order to the process of resolving the differing requirements of the running halls, we have assigned a "priority hall" for each day beam delivery has been scheduled. We outline here the meaning of priority and its effect on accelerator operations
The priority hall has the right to:
- require a re-tune of the accelerator to take place immediately when beam quality is not acceptable
- insist that energy changes occur as scheduled
- obtain hall access as desired
- request beam delivery interruptions for experiment-related operations such as Mott measurements of the beam polarization or pulsed operation for current monitor calibrations, temporarily blocking normal beam delivery to all halls. These interruptions shall be limited by a sum rule - the total time lost to the non-priority hall(s) due to such requests shall not exceed 2.5 hours in any 24-hour period. It is, of course, highly preferred that these measurements be scheduled at the morning meeting of the run coordinators whenever possible, and coordinated between halls whenever possible.
When the priority hall has requested a re-tune, if the re-tune degrades a previously acceptable beam for one of the other, lower priority running halls, then the re-tune shall continue until the beam is acceptable to both the priority hall and the other running halls that had acceptable beam at the time the re-tune began.
Non-priority halls can:
- require that a retune of the accelerator take place within 2.5 hours of the desired time (it will nominally occur at the earliest convenient break in the priority hall's schedule)
- require access to the hall within 1 hour of the desired time (again, it will nominally occur at the earliest convenient break in the priority hall's schedule)
- request Mott measurements in the injector within 2.5 hours of the desired time (it is preferred that this be scheduled at the morning meeting of the run coordinators and coordinated between the running halls whenever possible).
The ability of non-priority halls to request retunes and accesses shall be limited by a sum rule - the total time lost to the priority hall due to such requests shall not exceed 2.5 hours in any 24-hour period. (To facilitate more extended tuning associated with complex beam delivery, with the agreement of the run coordinators for all operating halls, the sum rule may be applied over a period as long as three days, so long as the average impact is less than 2.5 hours/day.) In the event that two non-priority halls are running, the 2.5 hours shall be split evenly between them in the absence of mutual agreement on a different split.
During operations in which the thermionic gun is being used as the electron source, when a non-priority hall needs changes to the accelerator state (re-tuning, access, etc.), then all halls currently receiving beam need to agree on the timing of the change and the shift leader for the priority hall should contact the crew chief to make the formal request. (The upgrades to the PSS and MPS system, together with the three-laser drive, eliminate the need for this constraint during normal operations using the polarized electron source. However, it may be necessary to reinstate it on a temporary basis in situation such as a laser failure in which we are forced to operate the polarized source in a non-standard manner.)
- can negotiate with other halls, and with the Accelerator and Physics Division for changes in scheduled energy changes (either direction)
Initial Tune-up of New Beams:
- Normally one shift is set aside for tune-up whenever a new beam setup is being tuned (for unusual beam setups more time may be scheduled explicitly for tuning at the discretion of the scheduling committee). It is understood that beam tune-ups shall always be done in the order in which the accelerator operations group believes will minimize the total time needed to tune all scheduled beams (i.e., the "priority hall" beam is not necessarily tuned first). In the event that obtaining the new beam setup requires more than the scheduled time, the Accelerator Program Deputy is authorized to spend up to one additional shift of tuning in an effort to deliver all scheduled beams instead of just the "priority hall" beam.
- Note that the setting of the Wien filter, which determines the polarization orientation in all halls, is NOT affected by the hall priority assignment. The Wien filter will be set to a value that maximizes the sum of the squares of the polarization delivered to all halls scheduled to receive polarized beam, and this setting shall be fixed throughout the running period unless all parties scheduled to receive polarized beam agree to a different setting.
Finally, any change in the accelerator schedule that has implications for running beyond one week and/or is not agreed to by the run coordinators for all affected experiments and the accelerator program deputy must be discussed and confirmed at meetings to be held (as required) each Tuesday and Friday afternoon at 4:00 in the office of the AD for Physics.
Facility Development Time
Experiments that do not get beam when scheduled, or which are unable to obtain the data required in the scheduled period due to problems with accelerator and/or experimental equipment availability will not be able to request a schedule slippage. However, the experiment may re-apply for additional beam time to complete the experiment at a later date. To facilitate the timely completion of experiments via this process, a period of about one week every two months or so has been put into the schedule for Facility Development. This time will be awarded by competition between experiments needing to complete data-taking, preparatory tests for future experiments, and testing new capabilities of the experimental equipment. This allows the schedule to be more rigidly adhered to (this has been a clear request from all users) but provides a degree of flexibility for unforeseen circumstances (this is, after all, an experimental program and things do not always go according to schedule). The schedule for the Facility Development periods will be determined at a meeting of the Scheduling Committee to be held one week before the start of the period. Requests for use of this time should be addressed to the Committee.
The schedule includes maintenance/development periods of 11 shifts every three weeks. They begin at 8:00 am on the day scheduled (nominally Monday). The initial half shift will be used for machine development work, focusing on studies of the beam transport lines to the halls. This implies that it may be necessary to keep one or more halls closed for this half shift, but all the halls may be opened after 12:00 noon.
It will be expected that the Physics ARMs will assist in opening the halls at this time. The rest of the day shift will be spent on diagnosing machine problems with the beam, to improve our ability to fix them the next day on the first try. This will be followed by a twoshifts of Injector studies, with some RF work done in parallel. Two shifts on Tuesday will be devoted to maintenance, followed by six shifts of machine development and beam restoration. It is expected that the halls will be locked up by 8:00 am on Thursday so that the beam can be properly tuned in each hall line. Beam will then be re-established to the experiment(s) by 12:01 A.M. on Friday morning. The details of the schedule are outlined in the table at the end of this section.
The machine development time will be used to prepare new experimental set-ups (such as polarization, non-standard energies,
three-beam operation etc.) needed for the immediate future as well as preparatory work for higher energy operation. On a few
occasions the maintenance period has been slipped a day in order to provide uninterrupted completion of a scheduled sequence of
measurements within an experiment. We cannot, however, eliminate or drastically reschedule these maintenance and development
New Maintenance/Machine Development Schedule (effective 2/00)
Week 1 of three-week cycle
|Owl||Physics||Injector||Hot Checkout by Ops (no beam)||Restore Accelerator
|06:00 Rad Survey
Software priority 12:00 - 20:00
MD on Hall lines
|12:00 Diagnosis||12:00 Restore Injector
23:00 Lock Halls
|Swing||Injector||Lock-up when work complete||Restore Halls
|Legend: Physics Running; Halls Locked for Accel. Use|
Weeks 2 & 3 of three-week cycle
12:00 Start Physics
- A major block of time for Maintenance and Machine Development will be scheduled for 11 shifts every three weeks, rather than 9 shifts every two weeks, our present schedule.
- The first four hours will be spent doing MD that requires beam to the halls.
- The halls will be open for experimental equipment maintenance from 12:00 on Monday through 23:00 on Wednesday.
- A designated period of time is provided for pre-maintenance diagnosis with beam (AES Group, Beam Physics & Instrumentation, and others) so that the maintenance time can be utilized effectively.
- Monday Swing and Tuesday Owl will be assigned to the Injector for the foreseeable future.
- There are two shifts for maintenance on Tuesday. It is anticipated that mechanical installations will start early and be finished around 6 pm. To avoid interference, the Software Group will have priority from 12:00 – 20:00 and the AES Group will have priority before 12:00 and after 20:00.
- The Wednesday Owl, "Hot Checkout by Ops," means that:
- System Owners need to write Hot Checkout procedures to be used by Ops.
- System Owners will be required to be physically present during Hot Checkout until procedures are provided to Ops.
- These procedures will be the basis for troubleshooting and repair documentation.
- Systems found to be defective will usually be fixed on the Wednesday Day Shift although major problems may have to be addressed immediately.
- Wednesday morning is available for completing installations and for final repair of systems found to be defective during Hot Checkout.
- The accelerator will be restored starting 12:00 on Wednesday, continuing through Thursday Owl. Some additional Machine Development may occur during these shifts.
- Restoration of beam to the halls will be done on Thursday Day and Swing shifts. This will include Machine Development on the hall beamlines, which would benefit from more dedicated time.
- On the weeks when no major maintenance is scheduled, 4 hours will be assigned on Tuesday morning. This will be used for recovering RF cavities to maintain a high active cavity inventory, and for tests of Beam Applications that would profit from frequent, short tests.
For holidays shown on the schedule (such as Thanksgiving) the beam will be shut down at ~noon on the last day shown as beam delivery (e.g. Wednesday noon before the Thursday Thanksgiving holiday). Beam operations for physics will be resumed at 8 AM on the first day after the holiday shown as beam operations, with the first shift devoted to beam restoration (i.e. it will be treated as initial tune-up of a new beam from the point of view of operations).
Energy Constraints on Multiple Hall Operations
The standard constraints for the different energies in the three halls during multiple hall operation are reiterated here for your information. The RF separators are able to extract one beam after each pass or, alternatively, to deliver beam to all three halls after five passes.
Therefore, it is always the case that:
- All three beams can have the same energy only on the fifth pass.
- No two halls can have the same energy, except on the fifth pass.
- Unusual beam energies in one hall will sometimes preclude multiple beam operation and impose shutdowns on the other halls, unless one or more of the other halls can also use a commensurate, unusual energy.
Polarization Constraints on Multiple-Hall Operations
A technical note covering all combinations of 2-hall polarized beam running is available (TN 97-021). Tables of ideal energies for two-hall operation and optimal energies for three-hall operation are available at the url:
You can also determine the dependence of the polarization in all three halls on the Wien filter angle for the actual settings of the accelerator.