E-beam tuning studies were done this week on beamline #1, primarily to identify quadrupole misalignment (evidenced by beam steering). Indeed, GQ8 (in the triplet upstream of the new wiggler) was found to be horizontally misaligned by ~0.5mm; Bob Harrington performed a precision adjustment that immediately provided improvement in the tune. Further improvements to the tune ideally require the use of the Smith-Purcell BPM’s, which are currently out of service. So, next week’s run (12/22) will hopefully include this; otherwise, continuation of wiggler modulation and the start of microbunch detection will occur.

Bob Harrington modified the CTR pop-in assembly to allow for more accurate alignment with direct HeNe beam. And, on the other side of the country, Wayne and Christian have been busy adding the high resolution BPM system to the ICA gas cell.

Many thanks go to all of the ATF & NSLS staff for their continuing help in bringing beamline #1 into a state of readiness. Their support has been crucial to the successes of STELLA.

A safe and happy holidays & New Year to all!

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VISA Experiment (REPORTED BY AARON TREMAINE)

This week we finalized the chamber and upstream beamline and bolted up. Currently, the system is pumping extremely slowly so as to reduce the probability of the undulator moving during initial pumpdown. Once we reach 10^-2 range, we will increase the pumping speed which will probably be early next week. An 8” T was inserted in place of one of the spool pieces (nipple between the chamber and one of the 4 ion pumps hanging from the ceiling) to allow addition of a 6” valve An extra turbo arrived from SLAC and has been worked on and should be ready to be used at the new valve thus, increasing the conductance greatly. The system will be leaked checked next week.

In the meantime, the cabling/controls are continuing. All the CAMAC modules have arrived and terminating the cables at the magnets, power supplies, actuator solenoids ...etc is continuing. This will be the main emphasis for the next few weeks. The BPM optical supports should be completed either today or Monday. Once completed, they will be installed in place. Next week the optics for the radiation transport from the experimental hall to the FEL room should arrive. Once here, we will need to redhead and then start mounting the transport (breadboards, mounts, optics, PVC pipe ...etc).

The steering magnets were mounted this weekend. It was found the tapped holes to mount them to table are placed to close to the BPM pop-in and hit the bolts on that flange. We will have to come up with another option the secure them to the table, but should not slow down the project. The steering magnets were found to be too strong. Using 16 gauge wire, it was found 12 turns could compensate the earth’s magnetic field with 750mA (~5mA with original magnets- can’t get this resolution with the controls). We have decided to put 30 turns around the already existing pole pieces, and use the original magnets for degaussing. This should give us enough strength to steer the beam through the undulator. If not, then we can easily switch to the original steering magnets.

The BPM optics holders will be finished this Wed. Once done they will be assembled and placed on the VISA table without optics. Don will start this as soon as we get these pieces from the main shop.

What we need to run:

1. Vacuum Pressure in mid 10^-7 range if not can run beam up to valve separating chamber from upstream beamline

2. Magnets (using Eurocrate),controls (have CAMAC cards here), DAC to control magnets , ADC to readback from magnets, TTL for magnet heat readback, cabling, from CAMAC to Eurocrate, from Eurocrate to magnets, cable is laid and being terminated

3. Pop-ins 32 solenoids, need power and air for controlling, have CAMAC cards here, cabling ,building breakout box, cable is laid and being terminated,airline, need calibration , put in actuator stops for BPM light to BPM optics, using alignment laser (has been propagated through undulator and out faraday cup)

4. Finish beamline from back of chamber to Faraday Cup

5. Flippers need for vs. length measurements alignment laser radiation interlocking not necessary for initial commissioning (can work on in off run days).

We must get items 1-4 finished. Our first scheduled run is for January 11 and 12.

We must remember this run is for final engineering of the BPM optics and for propagating the beam through the undulator which implies debugging all controls/data acquisition systems.

Another alignment in mid-Feb is tentatively scheduled and should be actively pursued.

This was Pedro’s last week of VISA work. He will be leaving BNL and kayaking to his native Cuba becoming a professional cigar roller for his uncle Fidel. He contributed much to the VISA infrastructure and his help will be missed.

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Feedback Systems(REPORTED BY VITALY YAKIMENKO)

A non-destructive charge measurement device – RF cavity – was tested this week. The signal from the cavity output was correlated with faraday cup at the end of the line. The correlation plot is shown at:

12_17_Cavity

We plan to install this device into H-line and use it to improve feed back system to compensate for changes in laser energy or quantum efficiency.

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Computer and Control System(REPORTED BY BOB MALONE)

VISA EXPERIMENT:

TTL input card for magnet power supply temperature interlock detection has arrived. It will be installed in the CAMAC crate located in CO2 room 3 and will be tested early next week.

STELLA EXPERIMENT:

Controls for two new pop-in monitors located before and after the STI wiggler have been installed. The monitors are designated GPOP_UP_2.3 (upstream) and GPOP_UP_2.6.

HGHG EXPERIMENT:

Additional ADC card to digitize the new diode array will be ordered and new software schemes will be developed to achieve synchronization in a variety of operating conditions.

FACILITY:

One-half day of operation time was lost on Thursday morning due to failure of the main power supply for the VAX. Compaq field service replaced the unit and the control system restarted for operations Thursday afternoon and evening. No system or user files were damaged as a result of this problem.

Note to network users:

A block of temporary IP addresses has been set aside for dynamic allocation (DHCP) by ATF users. Short-term visitors bringing computers to ATF need no longer make advance arrangements for a fixed IP address. Regular staff may also make use of these DHCP addresses while waiting for their application for a permanent IP address to be handled.

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Technical Operations (REPORTED BY BILL CAHILL)

As the new year approaches, the list of things to do in 1999 are dwindling quickly. The experiment hall cabling for the VISA “flight deck” steering magnets have been terminated by Aaron and Pedro. They were also extremely busy with the Eurocrate bi-polar power supplies, making up the interface wiring harness between the power supply and the controlling modules. Bob Harrington has assisted the VISA beamline with quadrupole realignments and the installation of a new pumping port. He has also been spending a considerable amount of time dimensionally mapping the terawatt laser discharge cell for engineering compliance. An unfortunate incident has cost us considerable time and effort concerning the loaned vacuum turbo from SLAC. Upon arrival at BNL, it was observed that the unit had not been packaged properly and during shipment, it suffered extensive damage. We found a broken vacuum snake, the bleed valve was bent and the oil mister can was broken. The NSLS Vacuum Group was generous enough to lend us a helping hand and upon inspection, found all of the rubber seals dry rotted. After two days of repair, the system appears to be functional. Marc is in the final stages of completion for the new RF low level I/Q modulator interface. End of the year safety and administrative reports were completed, and as always, the technical staff, aside from repair and assistance, must also maintain the position of control room duty operator. So here’s to us for a very busy and productive year. May the Gods shine upon us in the new millennium and pray for us all. We’ll need it! HAPPY NEW YEAR....

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Summary of the ATF Engineering Meeting(REPORTED BY XIJIE WANG)

1. ATF schedule: one issue discussed is the efficiency of ATF operations and experiments, especially experiments require CO2 laser, such as the HGHG and STELLA experiments. The overhead for switching experiments, such as testing synchronization and realignment, is significant if the switching is done too frequently. HGHG prefers two continuous days for every two weeks, while STELLA would prefer two-day per week for two weeks. Another subject is the ATF shutdown for maintenance, we prefer that the ATF users could also use this time for experiment upgrade.

2. YAG laser: Marcus was told laser oscillator was shipped this week, should be arrive here next week. Bob will make any parts required for the laser installation. Bill and Mark will be available for installation between Christmas and New Year. Past experience show that we must run the new laser ASAP, since we may have to send the laser back. We should keep the demo-unit at least until the end of February since the laser delivery was late for three months.

3. VISA experiment: A meeting was organized by Aaron to discuss the major issues for VISA beam commissioning. Responsibilities were clarified: Computer control: R. Malone, flipper for alignment laser shutter, actuator control, video switch and steering magnets. Install BPM optics, solenoid valve and airline: Aaron and Don. Terminate cables for Euro-crate power supply: Aaron and Pedro. Mark is responsible for the following projects on over time basis: finish actuators relay box and terminate cable inside the experimental. Bill will also help on the jobs inside the experiment hall.

4. CO2 laser: John presented an update on the status TW CO2 laser engineering review. To measure certain dimensions of the discharge cell, we may have to disassemble the electrodes. John estimates that Bob will finish the measurement in another day.

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Last Modified: December 3, 2007
Please forward all questions about this site to: Vitaly Yakimenko