21.Nov.01 M i n t y TTF OPERATIONS STATISTICS To direct accelerator improvements aimed at increased reliability, the operational statistics at the TTF are now logged on a per -shift basis. Initially these data were compiled to reveal outstanding hardware limitations. As reliability at the TTF continues to improve, correspondingly finer classifications have evolved. In the future, perhaps an automated analysis could be implemented. At present, the TTF operators are requested to the best of his/hers ability to classify the time spent during each shift into 1 of 4 categories: CATEGORIES: USERS - beam delivery for experimental programs using the intense SASE radiation (i.e. ABLO, Cluster, RAFEL) S TUDIES - all studies pertaining to accelerator development aimed towards quantification and improvement of beam properties (i.e. CSR, BTM, BBA, etc) and /or demonstrating TELSA-like beam conditions (i.e. high charge, high gradient, long pulses, etc.) TUNING - all time spent with beam providing the required condition for the users or accelerator development DOWN - downtime caused by hardware failure or anything else which prohibits operations (e.g. tours) A fifth category, time OFF, is also taken into account (i.e. arising from transitioning between SASE experiments e.g. ABLO/CLUSTER - and accelerator improvements) These statistics have been monitored since the end of the summer FEL conference (27.aug.01). Beam uptime, defined as beam hours allocated to the users, accelerator studies, and overall tuning, was on average 76% since August, 2001. Operational uptime, defined as uptime minus the time required for establishing the required beam conditions (tuning) was on average 51% during this time period. On average, hardware problems have inhibited experiments 24% of the time. The causes (and sought after remedies) are described next. The additional 27% decrease in the operational uptime (tuning) comprises accelerator reproducibility (i.e. recovering SASE after unexplained changes in the beam energy during beam delivery weeks) and setup time for the measurements of interest (during accelerator development weeks).
EXAMPLE: TTF operations 22.10.01 28.10.01 DOWN 25% OFF 0% USERS 48% TUNING 26% STUDIES 1%
TTF downtime summary (27.8.01 28.10.01) 3 6% 1%1%0%0%1% 0% 14% 17% 10% LASER GUN GUN VAC CC KLYS3 CRYO GUN&KLYS2 MAGS KLYS2 MOD2 UNKNOWN TOURS PD DIAGS VACUUM INTERLOCKS SERVERS MISSPULSE OTHER
ACCELERATOR DOWNTIME and improvements: LASER occasional charge instabilities (spare flashlamps on order) GUN sporadic events with high reflected energy and/or light flashes (cause unknown under study) GUN VACUUM sporadic vacuum events (cause unknown u n d e r s t u d y) CAPTURE CAVITY regulation (improved documentation?), to be eliminated KLYSTRON 3 (FOR THE GUN) DSP regulation errors (improvements ongoing) and, recently, reflected energy to the klystron (to be studied) CRYOSYSTEMS low Helium levels (ongoing concern switch to higher capa city HERA cryogenics plant in 2002) KLYSTRON 2 (FOR THE MODULES) primarily gun sparks ( s w a p t h e present test - klystron for another in Nov 2001) and DSP (improvements ongoing) and/or klystron phase regulation errors (improved setup procedure) TOURS - (inevitable) INAVAILABILITY OF PHOTON DIAGNOSTICS (FOR SFPD) almost trouble-free INAVAILABILITY OF OTHER DIAGNOSTICS (FOR MD) particularly the frame grabber software (transition to MACINTOSH -f r e e s o ftware successful) VACUUM SUBSYSTEMS (trouble- free) MAGNETS (trouble- f r e e ) INTERLOCKS (almost trouble-free) SERVERS particularly the gateway between FNAL klystrons and DESY DOOCS (fixed) MISSING PULSES (a new category overcomable with improved exception-h a n d l i n g in data acquisition, but nonetheless a serious issues arising predominantly from high RE events at the gun) OTHER (difficulties using the new electronic logbook)
OPERATIONAL DOWNTIM E During weeks devoted to beam delivery for SASE users, considerable time has been spent for tuning which involves the recovery of high - gain SASE following either a hardware fault or an unknown change in accelerator conditions (predominantly due to a change in beam energy). The following improvements have been made: hardware fault recovery implementation and (continued refinement) of state machines for the gun and module klystrons beam energy stability monitoring of the phase difference between the master oscillator and the LLRF phase reference (appears stable) independent monitoring of the vector gradients of the two accelerating modules In addition, missing pulses have been a concern. Missing pulses arise by intentional suppression of the beam by the beam interlock system (BIS) in response to a detected fault; e.g.. transmission loss. At present the primary cause for missing pulses is reflected energy at the gun. To minimize recovery time, the following changes have been implemented: reflected energy faults turn off gun rf drive only (not the modulator) a succession of 3 RE events (not 1) is required In the future, tuning time may begin to include time spent on transmission optimization for long pulse operations. 25.10.01 Some comments during presentation: in the future performance statistics should also be logged as the hardware (bunch counters, SASE gain indicators) becomes available - this work is in progress by D. Noelle et al (opening remarks by MM) it may be useful to also specify the number of occurrences - downtime caused by the laser and the capture cavity was dominated by a single-occurrence event (contributed by H. Weise and M. Ross) one might consider not including time lost due to tours in the downtime category pro: no association with a hardware fault con: prevention of beam delivery and/or accelerator studies (contributed by P. Schmüsser)