PROCEDURE: 9s TITLE: SBC safe-open, diffuse illumination. CATEGORY: verification PURPOSE: This set of procedures provides a means to open the SBC when the amount of UV flux has not yet been verified. There are two variants. One for when the the illumination pattern is not known, the other for when the illumination pattern is known, but the absolute flux level is not. FREQUENCY: Run once before using each lamp, and variant b whenever the amount of illumination onto the SBC changes. DETECTOR: SBC PREREQUISITES: Although the exact illumination pattern need not be known, this procedure is optimized for diffuse illumination. It will not work well for point source illumination. Model predictions of count rates for all lamps. List of available attenuations for STUFF. HARDWARE REQUIREMENTS: STUFF for external illumination. SOFTWARE REQUIREMENTS: Insure that SITS terminal is set to monitor _calibrated_ global count rate. COMMAND MODE: PSTOL OVERVIEW: The illumination onto the SBC is determined by the light path as follows: lamp : lamp intensity : lamp-attenuation : modulator : SBC filter : SBC (<---- environment ---->) Where: 1. lamp is the illuminating source: STUFF - PtNe1, PtNe2, Xe1469, Kr1236 internal - D2 2. The lamp intensity may be a variable. If so hopefully it is controlable 3. lamp-attenuation STUFF - a variety of mesh filters internal - ND filter - fixed 4. modulator STUFF - various pinholes (Xe1469, Kr1236) The pinhole stage position also matters, since the lamps will have bandpass filters halfway obscuring them. - spectralon, MMA (PtNe1, PtNe2) internal - cal door, coronographic arm, M3 mirror 5. SBC filter - F122M, F165LP, F150LP, F140LP, F125LP, F115LP, PR130L, PR110L, block filters 6. SBC - the detector. 7. Environment - ambient, N2 purge (wide range of efficiencies), or vacuum. Of these, the two factors effecting the illumination _pattern_ are: the lamp (1), and the modulators (4). The other items mainly effect the illumination level The first time the SBC sees light for a given combination of lamp and modulator, the opening to light must be very careful. At the start the SBC is powered up, the cal door is closed, the M3 mirror is set to the HRC position. The lamp attenuation, lamp intensity and/or the SBC filter should be set to levels expected to produce safe-illumination when all internal modulators are removed. Then the cal door is opened and the block-filter removed. The M3 is slowly stepped to the SBC position, with the global count-rate noted along the way. If, along the way, the global count-rate exceed the global count rate limit (2.9e5 c/s), the procedure is stopped. Then, if possible, a safer combination of intensity, attenuation, and SBC filter should be employed, and the procedure be run again. The data collected in the first pass will be used to derive a curve of fraction of illumination vs. M3 position. This can be used for a quicker safe-open. I.e., opening in only a few M3 positions. PROCEDURE/EXPOSURES: VARIANTS: A- General Full Safe Open ~~~~~~~~~~~~~~~~~~~~~~~~~ 1. Block filter in place 2. M3 in HRC position 3. Cal door closed 4. Insure that SITS terminal is set to monitor _calibrated_ global count rate as JMEVENTS. Specifically, JMEVENTS should give the total counts over a 0.1s interval (i.e. it lists 1/10 the global count rate). 5. Power-up SBC (if not already done) 6. If using external illumination, a. Adjust source to expected safe level. b. Note configuration of source (e.g. STUFF, PtNe1 I = 10mA, ND Filt # 3, MMA), in SBC safe open log file (see blank and example attached below). 7. If using internal D2 lamp, turn it on and wait for it to warm up (nominally 7 minutes). 8. If external illumination, open Cal Door. 9. Put desired SBC filter in place, note filter in safe open log file. 10. Note JMEVENTS at this position in safe open log file as first entry of table. 11. Open M3 mirror in steps using JFOLDREL while monitoring JMEVENTS at the SITS terminal. a. At each step, note in safe open log file table (1) JFOLDREL, (2) the sum of all previous JFOLDREL commands - this gives the absolute M3 position, and (3) JMEVENTS. b. If JMEVENTS => 30000 then the global count rate is >3e5 Hz. Put block filter in place and put M3 to the HRC position. Note final M3 position, and JMEVENTS in safe-open log. Do not open again with this illumination pattern unless external attenuators and/or SBC filter have been adjusted to produce a lower count rate on the MAMA. c. The actual M3 positions to be sampled is at the discretion of calibration test conductor, with the following factors considered: * The range of M3 positions should go from 0 (HRC) to 120 (SBC), inclusive (unless JMEVENTS => 30000 along the way). * This should be done preferabley in at least six JFOLDREL steps, all positive. * The first 20-30 M3 steps, and the last 20-30 steps may see very little change in JMEVENTS as the M3 mirror fully blocks and is fully out of the beam respectively, hence positions in these ranges may be skipped. * Fine spacings (e.g. 5-10 M3 steps) are called for when the M3 mirror first starts to let light to the SBC and if JMEVENTS is very large (> 10000). * The STUFF pinholes (especially the 1mm pinhole) will effectively have a very slow beam and hence sharp edges. Very fine steps (2-5) are called for when first encountering the beam edge. * Unless JMEVENTS => 30000 is reached before-hand, the last step should bring the M3 mirror to the SBC position. Be sure to record JMEVENTS at this position in the safe open log file. * A suggested set of JFOLDREL commands are as follows JFOLDREL Sum(JFOLDREL) 0 0 (HRC) 20 20 10 30 5 35 5 40 5 45 5 50 10 60 20 80 20 100 20 120 (SBC) d. If M3 reaches the SBC position with JMEVENTS < 30000 - congratulations you have safely opened the SBC! 12. Now calculate fractional illumination for the M3 positions that have been sampled and note in safe-open log sheet. 13. A copy of the safe-open log file should be kept with the SITS operator, and another should be kept with the ACS science team. B- General Abbreviated Safe Open. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1. Block filter in place 2. M3 in HRC position 3. Insure that SITS terminal is set to monitor _calibrated_ global count rate as JMEVENTS. Specifically, JMEVENTS should give the total counts over a 0.1s interval (i.e. it lists 1/10 the global count rate). 4. Power-up SBC (if not already done) 5. If using external illumination, a. Adjust source to expected safe level. b. Note configuration of source (e.g. STUFF, PtNe1 I = 10mA, ND Filt # 3, MMA), in NEW SBC safe open log file (see blank and example attached below). 6. If using internal D2 lamp, turn it on and wait for it to warm up. 7. If external illumination, open Cal Door. 8. Look through previous full safe-open log files for an opening that matches the illumination pattern of the current conditions. That is it must have a. The same or similar lamp (defined as one that will produce a very similar illumination pattern. E.g. with STUFF, PtNe2 instead of PtNe1, or Kr1236 instead of Xe1469, but NOT PtNe1 instead of Kr1236). b. If an external source, the same external modulator. The lamp attenuator, current, and SBC Filter may be different. However, the set up should be such that the final opened count-rate should is expected be within or very near the safe range of <= 3e5 Hz integrated over the detector. This can be ascertained by scaling previous results with model calculations. 9. Put desired SBC filter in place, note filter in NEW safe open log file. 10. Note JMEVENTS at this position in NEW safe open log file as first entry of table. 11. Use old full safe-open log file as a guide to opening M3 to SBC in four JFOLDREL moves as follows. a. The four steps will correspond to fractional illuminations of in turn of ~0.05, ~0.25, ~0.50 and 1.00. b. Pick the M3 positions in the old log file that correspond most closely to these fractional illuminations, and calculate the JFOLDREL movements required to get there. c. At each M3 position record JMEVENTS and estimate whether the next move can be made safely using the old safe-open log file as a guide. d. Only make the next movement if the prediction is that it is safe to do so. e If not, abort the safe-open: * put block filter in place * M3 to HRC position. do not open agin with this illumination pattern unless the illumination intensity is decreased (using lamp current, attenuators, or SBC filter). 12. Calculate fractional illumination at M3 positions used in this opening and compare to old results. Note any severe discrepencies (>20%). 13. Return old log file to SITS operator (if that is where you got it), and file new log with SITS operator and ACS science team. TOTAL EXPOSURES: n/a TOTAL TIME: A. Full open <~ 1 hour. B. Abbreviated open <~ 0.5 hour. ANALYSIS: Fill out SBC safe open log, calculate fractional illumination. ATTACHMENTS: 1. blank safe open log file. 2. example safe open log file. ________________________________________________________________________ # SBC safe-open log file. # # Date : # Environment : # Source : # Lamp : # Current : # Voltage : # Attenuation : # Modulator : # PMT reading : # SBC filter : # # Opening type : # # Notes - JMEVENTS from SITS terminal. It should correspond to # calibrated count rate. # - frac. illum = (JMEVENTS(M3) - JMEVENTS(0))/(JMEVENTS(120) - JMEVENTS(0)) # this should be filled out by the calibration scientist. # - If JMEVENTS > 30000, insert block filter, put M3 to HRC position. # # ------------------------------------------------------------------------- # Absolute M3 pos # JFOLDREL SUM(JFOLDREL) JMEVENTS frac. illum 0 0 0.0000 # M3 = HRC must record 120 1.0000 # M3 = SBC must record ________________________________________________________________________ # SBC safe-open log file. # # Date : Dec 15, 1998 # Environment : N2 Purge # Source : STUFF # Lamp : PtNe1 # Current : 20mA # Voltage : 0.2 KV # Attenuation : 0 # Modulator : MMA # PMT reading : N/A # SBC filter : F115LP # # Opening type : FULL # # Notes - JMEVENTS from SITS terminal. It should correspond to # calibrated count rate. # - frac. illum = (JMEVENTS(M3) - JMEVENTS(0))/(JMEVENTS(120) - JMEVENTS(0)) # this should be filled out by the calibration scientist. # - If JMEVENTS > 30000, insert block filter, put M3 to HRC position. # # ------------------------------------------------------------------------- # Absolute M3 pos # JFOLDREL SUM(JFOLDREL) JMEVENTS frac. illum 0 0 3 0.0000 # M3 = HRC must record 25 25 550 0.0227 5 30 1733 0.0719 5 35 3952 0.1642 5 40 6890 0.2863 5 45 10624 0.4415 5 50 14496 0.6025 5 55 17861 0.7424 5 60 21110 0.8741 60 120 24059 1.0000 # M3 = SBC must record