Commissioning goals -- June 1995 Distributed 12 June 1995 ================================ Dear CALCOM Friends: As you all know, the upcoming CLAS collaboration meeting in Richmond will focus on "Commissioning" aspects of the CLAS detector and hall B. The following TEX file is aimed at describing some of the objectives, and steps in the CLAS commissioning. Eventually, we will have to develop detailed procedures for the commissioning of hall B that should be described in the CALCOM Handbook. Please review the text, and make comments for improvements, and send them to me before the meeting. Dan S. has already made improvements over the original text. I hope we can discuss the modified version of this document at the collaboration meeting. Volker %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \magnification \magstep 2 \centerline{D R A F T - Mod. DS 9-Jun-95} \vskip0.5cm \centerline{\bf COMMISSIONING THE} \centerline{\bf HALL B EXPERIMENTAL EQUIPMENT} \vskip1.0cm \centerline{\bf INTRODUCTION} \vskip6pt The main instrument in Hall B is the toroidal multi-gap spectrometer CLAS (CEBAF Large Acceptance Spectrometer). The approximately toroidal magnetic field distribution is generated by six iron-free superconducting coils. The particle detection system consists of drift chambers arranged in three regions (region 1, region 2, region 3) to determine the trajectories of charged particles, Cherenkov detectors for the identification of electrons, scintillation counters for time-of-flight measurements, and electromagnetic calorimetry to identify electrons and to detect high energy photons and neutrons. The six sectors are instrumented individually to form six independent spectrometers. This is a good basis for achieving operation at high luminosities and high count rate capability. The region 1 drift chambers are located in the field-free region around the target. In order to protect the chambers from charged electromagnetic background emerging from the target, a small normal-conducting toroidal magnet will be installed around the taget area. The coils of this magnet will be located entirely within the shadow region of the large torus and will not contribute to additional obstruction of solid angle. The main components of CLAS in their conceptual stage, their functions in CLAS, and their expected performance, are described in the Conceptual Design Report (CDR)[1]. The CDR is the basic document used by the CLAS collaborators to design specific experiments. One of the goals of the commissioning of CLAS and the other Hall B equipment is to verify that these design goals can be achieved, and possibly exceeded in real experiments. \vskip6pt Calibration procedures which do not require beam operation (e.g. TDC \& ADC calibration, laser calibration, and cosmic ray measurements) are not part of this commissioning plan. It is assumed that these procedures have already been completed before commissioning. Cosmic ray dalibration data of the complete detector system can be taken during down time periods of the accelerator. \vskip12pt The commissioning of CLAS and Hall B is assumed to be a collaborative effort of the entire CLAS collaboration, with shift plans for around-the-clock operation, and a full committment of the collaboration to complete this phase in an efficient and timely fashion. It is assumed that Hall B instrumentation is operational, and that the software for calibration and analysis has been developed. \vskip6pt \itemitem{-} CLAS Torus operational \itemitem{-} Mini torus operational \itemitem{-} Beam pipe in place \itemitem{-} Beam position monitors operational \itemitem{-} Faraday cup operational \itemitem{-} Beam raster magnets operational \itemitem{-} Thin targets and long gas/liquid target available \itemitem{-} CLAS detectors operational (preferentially all, but can live with incomplete detector installations) \itemitem{-} Tagger system operational \itemitem{-} Trigger (level 1) and DAQ system operational \itemitem{-} On-line control system operational \itemitem{-} Minimal slow control (high voltages, DC gas system, Cerenkov gas system, beam monitors) operational \itemitem{-} Calibration software, on/off-line analysis software available \vskip24pt \centerline{\bf 2. OBJECTIVES} \vskip12pt \noindent {\bf 2.1 General} \vskip6pt In general, the objectives of the Hall B commissioning procedure are to achieve reliable beam transport through thin and extended targets to the beam dump, to verify the optics design of the CLAS torus magnet, to determine the alignment and operational performance of the CLAS detector systems and the photon tagging system using beam interactions, and to perform those calibration procedures which require operating the electron beam. Operation of the CLAS detector system in conjunction with the trigger and data acquistion system and other ancillary systems will be studied as well. \vskip6pt After completion of the commissioning, the Hall B instrumentation, including the beam line, the CLAS torus magnetic field distribution, all CLAS detectors, the photon tagging system, the trigger and data acquisition systems, as well as the CLAS software, will have been checked out and calibrated with sufficient accuracy to allow the accumulation of data and their first pass analysis for all experiments in the first year of CLAS running. Table 1 shows the CLAS running period schedule. \vskip16pt {During the commissioning period no attempt will be made to produce physics data for publication. This is meant to assure that commissioning procedures be carried out based on nessecities and logical sequences of activities. The tagger commissioning may be an exception if it is decided that experiment g5 be conducted as part of the tagger commissioning. This could imply putting the tagger commissioning at the end of the commissioning phase of Hall B.} \centerline{\underbar {Table 1: CLAS Running Period Schedule}} \vskip12pt \settabs \+xxxx&xxxxxxxxxxxxxxxxxxxx&xxxxxxxx&xxxxxxxx&xxxxxxxx&xxxxxxxxxx\cr \+&&Run&Early&Middle&Late\cr \+&\underbar{Commissioning}&\underbar{Period}&\underbar{Days}&\underbar{Days} &\underbar{Days}\cr \vskip6pt \+&about 6&g1&~32&~16&~17\cr \+&Months&g2&~14&~14&&\cr \+&(includes 10&g3&~14&~~7&~~7\cr \+&days of g5)&g6&~~7&~15&&\cr \+&\cr \+&&e1&~42&~41&~41\cr \+&&e2&~20&~20&&\cr \+&&e5&&~10&~10\cr \+&&eg1&&~51&~52\cr \vskip3pt \+&Total Days&&129&174&127\cr \vskip12pt \noindent {\bf 2.2 Requirements} \vskip6pt The list of experiments of year 1 may be subject to change (PAC9 results have not been implemented, PAC10 response to the CLAS collaboration running plan, etc.). Presently ($<$ PAC9), year 1 of running includes significant fractions of nearly all approved experiments using CLAS, with the exception of experiments requiring polarized targets (eg1), or other non-standard target setups (e5). Therefore, the commissioning requirements for year 1 may already be as stringent or nearly as stringent as they will ever get. \vskip6pt The following two tables summarize these requirements, as they are presently known. These are the result of the questionaire distributed before the CLAS collaboration meeting, March 1995, and may be subject to change. \vskip16pt \centerline{Table 1: Minimum requirements for average reconstruction errors} \vskip12pt \settabs \+xxxxxxx&xxxxxxxxxxxxxxxxx&xxxxxxxxxx&xxxxxxxxxx&xxxxxxxxxx&xxxxxxxxxx&xxxxxxxxxx\cr \+&Kin. Quantities & {$\Delta\theta$} & {$\Delta\phi$} & {$\Delta p/p$}&{$\Delta t $} \cr \+&& mrad&mrad&\%&nsec\cr \vskip6pt \+&Inc. Electrons& -&-&0.05&-\cr \vskip3pt \+&Scatt. Electrons& 0.5 & 1. & 0.1 & - \cr \vskip3pt \+&Charged Hadrons&1.0 & 1.0 & 0.1 & 0.15 \cr \vskip3pt \+&Photons&5.0&5.0&1.0& - \cr \vskip3pt \+&Neutrons&15&15&-&0.1 \cr \vskip16pt \centerline{Table 2: Maximum uncertainties (\%)} \vskip12pt \settabs \+xxxx&xxxx&xxxxxxxxxxxxxxxxxxxxxxx&xxxxxxxx&xxxxxxxx&xxxxxxxx&xxxxxxxx\cr \vskip6pt \+&Detection efficiency\cr \vskip3pt \+&&Electrons& 1.0\cr \vskip3pt \+&&Charged Hadrons& 1.0\cr \vskip3pt \+&&Photons& 2.0\cr \vskip3pt \+&&Neutrons& 1.0 (Run period e5)\cr \vskip6pt \+&Integrated Luminosity&& 2.5\cr \vskip12pt The following subsections 2.2.1-2.2.7 summarize the objectives grouped logically by sub-system. Section 3 gives an outline of the steps required in approximate chronological order. \vfil\eject \noindent {\bf 2.2.1 Beam line operation (unpolarized beam/target)} \vskip12pt \item{a.} {\sl Optimize the beam transport through the hall and the CLAS to the Faraday cup and/or the beam dump at various beam currents, without and with nuclear targets. This will be repeated for various beam energies and beam currents.} \vskip6pt \item{b.}{\sl Determine the accuracy, stability and reproducibility of the beam monitors.} \vskip6pt \item{c.} {\sl Verify beam parameters such as spot size and angle dispersion using beam position monitors.} \vskip6pt \item{d.} {\sl Establish background levels from the beam dump and/or Faraday cup for optimized beam parameters. Develop optimal shielding conditions of the tunnel at various running conditions.} \vskip6pt \item{e.} {\sl Calibrate the current integrator (Faraday cup) at various beam energies and beam currents.} \vskip12pt\noindent {\bf 2.2.2 Beam line operation (polarization experiments)} \vskip6pt \item{a.}{\sl Establish the operation of the M\"oller polarimeter using unpolarized beam at different energies and different target foils.} \vskip6pt \item{b.}{\sl Establish the operation of the beam line "Raster Magnets" in front of the M\"oller polarimeter, and in front of CLAS (for polarized target operation). } \vskip12pt\noindent {\bf 2.2.3 Photon tagging system} \vskip6pt \item{a.}{\sl Establish the operation of the photon tagging system.} \vskip6pt \item{b.} {\sl Establish optimal sizes and positions for the photon beam collimator(s) at various running conditions.} \vskip6pt \item{c.}{\sl Establish the operation of the total absorption counter and the pair spectrometer.} \vskip6pt \item{d.} {\sl Perform an energy calibration of the system for different incident electron beam energies.} \vskip12pt \noindent {\bf 2.2.4 CLAS operation} \vskip6pt \item{a.} {\sl Study the performance of the CLAS detector systems and the trigger and data acquisition system at different beam/target conditions.} \vskip6pt \item{b.}{\sl Verify the detector alignments by operating CLAS without magnetic field at very low beam currents and using thin targets.} \vskip6pt \item{c.}{\sl Calibrate the various CLAS detector system using beam interaction in thin and/or extended targets, and various field settings in the CLAS torus magnet. (This includes establishment of trigger and detection efficiencies of the various detection systems.) } \vskip6pt \item{d.} {\sl Checkout the CLAS calibration and reconstruction software.} \vskip12pt\noindent {\bf 2.2.5 System integration} \vskip6pt \item{a.} {\sl Test the operation of CLAS in conjunction with other Hall B equipment and beam line instrumentation components} \vskip24pt \centerline{\bf 3. BASIC STEPS} \vskip12pt Where references are given, e.g. "[section X.Y]," these refer to sections in the CLAS CALCOM (calibration/commissioning) HANDBOOK (to be written), where details regarding objectives, technical procedures, additional hardware needed, estimated required beam time for specific tasks, required software support, responsibilities, etc. should be compiled. {\it To provide these details is the responsibility of the various subgroups.} \vskip12pt \item{3.1} Transport low-current beam (in the range from 1 nA to 1 $\mu$A) to the beam dump and/or Faraday cup without passing through a scattering target. This should accomplish \vskip6pt \itemitem{a.} {\sl tests of the beam-line instrumentation [section 8.1]} \itemitem{b.} {\sl the initial low-power test of the beam dump and the Faraday cup} \itemitem{c.} {\sl determine/optimize the background situation [section 8.2]} \vskip6pt \item{3.2} Install a `thin' target, and transport beam on and through the target to Faraday cup and/or dump [section 8.3]. \vskip6pt \item{3.3} Conduct initial test of the CLAS with scattered beam, including: \vskip6pt \itemitem{a.}{\sl Performance tests of the toroidal shielding} magnet ("mini-torus") [section 8.4]. \itemitem{b.}{\sl Preliminary tests of the on-line control system } [section X.1]. \itemitem{c.}{\sl Preliminary tests of the trigger and data acquisition system [section 7.1]}. \itemitem{d.} {\sl Preliminary performance tests for the drift chambers [section 2.1], the time-of-flight detectors [section 3.1], the gas Cerenkov detectors [section 4.1], and the electromagnetic calorimeters [section 5.1]}. \vskip6pt \item{3.4} Mount an extended target (high pressure gas or liquid) and transport beam through this target to Faraday cup and/or beam dump [section 8.5]. \vskip6pt \item{3.5} Test CLAS operation with extended target [section 8.6]. \vskip6pt \itemitem{a.} {\sl Test performance of the toroidal shield under realistic beam conditions [section 8.7]}. \itemitem{b.} {\sl Test performance of the drift chambers section [section 2.2], the time-of-flight counters [section 3.2], the gas Cerenkov detectors [section 4.2], and the electromagnetic calorimeters [section 5.2] at various luminosities (beam current $\cdot$ target thickness) by varying the beam current, and at various energies (e.g. 0.8, 2.4 and 4 GeV)} \itemitem{b.} {\sl Test the trigger system [section 7.2], at various luminosities.} \itemitem{c.} {\sl Test the data acquisition system [section 7.3] at various luminosities.} \itemitem{d.} {\sl Test the on-line display and analysis software.} \vskip6pt \item{3.6} {Conduct detector calibration} at zero field with beam interaction and thin targets. \vskip6pt \itemitem{a.} {\sl Install additional hardware (if needed), e.g. a calibration target for region I drift chambers or a slit system, to verify the detector alignments.} \vskip6pt \itemitem{b.}{\sl Verify drift chamber [section 2.3], time-of-flight system [section 3.3], and calorimeter [section 5.3] alignments with beam interactions at zero magnetic field setting in CLAS torus and in the mini-torus.} \vskip6pt \item{3.7} Conduct detector calibration with magnetic field and beam interaction. \vskip6pt \itemitem{a.} {\sl Test calibration trigger control system [section 7.3]. \itemitem{b.} Minimum ionizing calibration of time-of-flight [section 3.4] and calorimeter systems [section 5.4], with CLAS torus OFF, but mini-torus ON. \itemitem{c.} Turn on the magnetic field in the torus and the mini-torus and repeat measurements. This will check the reconstruction of the target vertex point. \vskip6pt \item{3.8} Detector calibration with beam interaction and extended gas targets at various CLAS field settings using exclusive reactions. This may require that specialized triggers be available to allow determination of detection efficiencies in the TOF system, the CC detectors, and the EC detectors [sections 2.5, 3.5, 4.5, 5.5].} \vskip6pt \item{3.9} {\sl Test {limitations of the detector performance}, the trigger and data acquisition systems, by varying the beam intensity [section 7.5].} \vskip6pt \item{3.10} {Determine detector performance for various nuclear targets and verify the effectiveness of passive shielding arrangement [sections 8.8 ].} \vskip6pt \item{3.11} Test operational performance of the tagging system using radiator foil in front of the photon tagging system [section 6.1]. \vskip6pt \itemitem{a.} {\sl Transport low current (1 nA to 1 $\mu$A) to the beam dump.} \itemitem{b.} {\sl Energize the tagging magnet and transport beams at various energies to the tagging beam dump.} \itemitem{c.} {\sl Verify operation of tagging detectors - energy and timing counters, at various beam currents and energies} \itemitem{d.} {\sl Test background conditions in CLAS without scattering target.} \itemitem{e.} {\sl Optimize photon beam collimators for operation at various energies, and determine beam size and position at the production target location in CLAS.} \itemitem{f.} {\sl Test photon beam instrumentations, the pair spectrometer, and total absorption counter (if available).} \itemitem{g.} {\sl Mount `thick' solid target in CLAS and test operational performance of the CLAS detectors, the trigger system and data acqisition system.} \itemitem{h.} {\sl Mount liquid cryogenic target in CLAS and test operational performance of the CLAS detectors, the start counters, the trigger system and data acquisition system.} \vskip6pt \item{3.12} {Establish operation of tagging system in coincidence with the CLAS detector components. \vfil\eject The CLAS collaboration has to: \vskip16pt \item{$\bullet$} agree on the objectives and scope of the commissioning phase. \vskip16pt \item{$\bullet$} make the commissioning phase an important part of its activities, e.g. by planning the commissioning of subsystems at the technical working group meetings \vskip16pt \item{$\bullet$} define details of the commissioning tasks for the subsystems and write respective sections of the CALCOM handbook, and identify responsibilities \vskip16pt \item{$\bullet$} agree on a time line for the commissioning phase \vfil\eject\bye