2002: STACEE-64 is complete!
See below for a summary of the work completed. Right now our future plans call for essentially full time sceince observation and analysis for the next three years at least.
For a complete summary of the current staus of the STACEE experimental program, including instrument details, publications, and science motivation, see the main STACEE Collaboration Home Page at UCLA
1999-2001: STACEE-48 and work towards STACEE-64
Construction of STACEE continues. STACEE is expanded and improved in several key areas:
Optics
STACEE expands the number of heliostats used in the field to increase teh overall light collection area, to achieve a more uniform sampling, and to reduce the energy threshold of the experiment. The expansion will take place in two steps: First we added a third secondary mirror to the current platform to collect light from an additional 16 heliostats in the north central region of the heliostat array. This is called STACEE-48. Construction of the second step was to add two smaller secondary mirrors (single piece 1.1-meter diameter) at a lower level on the tower to collect light from another 16 heliostats located in the south central section of the array. The resultant configuration will be called STACEE-64 with a total of 64 heliostats. This work is scheduled for 2000-2001. The two figures below indicate the arrangement of the current and future heliostats and secondary mirror systems:
Current and future heliostats used in STACEE
Current and future secondary mirror systems mounted to the central tower to collect light from heliostats for the STACEE experiment. The height of the tower is approximately 200 feet.
Electronics Upgrade
There are three major upgrades that were done during this interval.
- We migrated from a CAMAD-SGI based trigger and data acquisition system to a faster and more erliable VME-based system.
- For the trigger, we replaced the digital delays with a custom VME-based trigger/programmable delay unit.
- Most importantly, we installed a set of fast Flash ADC's (digitizers) (1Gs/sec) to record directly the pulse profile from each channel. These digitizers allow us to determine the timing and amplitude of each Cherenkov light pulse to high precision needed to accurately reconstruct the air shower.
These upgrades were done 1999-2001. The figure below shows a schematic arrangement of the new STACEE electronics system.
Electronics upgrades for STACEE in 1999-2000
1998: STACEE-32
Construction of the STACEE experiment is ongoing and has been taking place since early 1998. By November of 1998, we had completed a partial version of STACEE using 32 heliostats located in the east and west corners of the array. This arrangement, called STACEE-32, included 32 photomultipliers, sixteen each in two cameras located at the 260-level of the central tower. Data from each camera was recorded using standard CAMAC multi-hit TDC's and ADC's.
We conducted extensive tests and observations using STACEE-32 during the period from November 1998 to June 1999. Our two main objectives were (1) Collect a large amount of "engineering" data (mostly observations with the heliostats tracking the zenith) to determine various instrument performance properties and calibrations, and (2) Observe the Crab Nebula and Pulsar as much as possible. The Crab represents a "standard candle" of sorts, having been detected by previous experiments as a steady source of gamma-rays at energies both below and above the STACEE energy window.
By summer of 1999, we had analyzed the data taken from the Crab. Our results have been presented at various conferences (see especially our presentation at the TeV Workshop). STACEE detects the Crab with a high significance (7 sigma) at an estimated energy threshold of 70 GeV. This result demonstrates the viability of the STACEE instrument.
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