See:

4_21_STELLA_nwig1 4_21_STELLA_nwig2 The local team, with the help of the ATF (thanks also to Don Davis), was able to prepare the entire beamline in less than one week for the latest beam studies run (held Thursday).  Igor and Karl aligned the HeNe laser to all BPM’s on the line which then allowed Vitaly to very accurately position the e-beam and steer through both wigglers.  Transmission was excellent to the end of the beamline (spectrometer) with a large charge (0.5 nC), and was achieved rather quickly.  No problems with the new wiggler were encountered, so we consider it ready for the three-day run next week.  Wayne & Christian from STI will again be at BNL to work with the local team, starting Sunday with final CO2 laser alignment.  Delivery of picosecond CO2 to both wigglers with rough synchronization to the e-beam will be our first agenda item for Monday.

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Here are the results from last week’s run in PDF format:

4_21_VISA

(Credit to the drawing of the undulator/magnets are to go to the great Alex “Kandinsky” Murokh!)

For our next two run days, we are going to solely study the trajectory and how to improve it by correction algorithms using the two upstream steering magnets.

We believe we have a good plan for separation of the spontaneous from the OTR in the BPMs using polarizers and filters.

The transport is still being installed and should be finished once again, by Monday.

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We (S. Kashiwagi, B. Malone, X-J Wang, V. Yakimenko) have performed Longitudinal Tomography Study on April 20^th 2000 evening. At the first, we checked the data taking program of Mathcad. Bob found some bugs in my program to save an image using the Frame Grabber system and we fixed them.  After that, we started to take data.

In this beam study, the maximum beam energy was about 60 MeV.  We changed the rf-gun phase by four steps, each phase is 5 degree different (210~225 degree). At the each step, we measured the bunch charge and the longitudinal phase space distribution using tomography technique. Due to the Schottky effect, the bunch charge was different at each step and the bunch length was also different. Now I am analyzing this experimental data. From this measurement, we will be able to clear the relation between the bunch length and longitudinal emittance (distribution). Finally we will compare with simulation and beam experiment. 

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The maintenance this Monday involved several miscellaneous tasks that had been accumulating for several weeks:

1)   Debug and restore UV Joulemeter and camera in YAG room to operation:

Minor realignment and cabling.

2)   Debug 1.5 Hz phase noise observed on phasemeter: This was an artifact traced to an oscilloscope ground loop.

3)   Test Gaussian reflectors: These were manufactured improperly, new pieces will be delivered. The pieces in hand may still be usable in another configuration, but more testing is required next week.

4)   Cathode profile improvements:  Tried to optimize beam location in fourth harmonic crystal and cleaned UV optics, but profile still shows modulation.

The rest of the week the system ran for experiments without realignment.

As usual, the laser’s performance is summarized under

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Monday Maintenance Day involved the opening of the gun clamshell and tuning for field balance with the network analyzer borrowed from the good folks at the 200 MeV Linac. Plant Engineering also took advantage of our downtime and installed the new a/c unit for the Klystron enclosure. NSLS electrician’s installed the ac power and all was a go. Tuesday brought a different story, the a/c unit was energized and it was found that the fan only operates on “fan only”. The compressor operates but does not blow the cold air.  Unfortunately, it is extremely difficult to remove the unit due to tight quarters in and around the Klystron area, whereas, Plant Engineering will have to bring the man-lift back to Bldg.820 and remove the entire insert. As HGHG was operating in the latter part of Tuesday, The gun solenoid became inoperable. The problem appeared to be water flow or lack of it, the water circulator was swapped to increase the volume but didn’t help.  The experiment shut down and upon investigation on Wednesday, the clamshell was reopened and we found the over-temperature sensor tripped.  Apparently, the smaller chiller unit does not have enough flow to compensate for the heat load. A new unit is on order. An optic flipper in the YAG/gun hutch failed and had to be repaired, RF instability warranted an investigation of the low level system and we found a broken connector on the phase meter.  After replacement, all is well. Parts gathering and assembly is still the household word for the Linac water system, Bob Harrington continues with the YAG amplifier and pre-amplifier water system modifications. Much effort is being invested in safety and training, Marc has re-certified as “Rad Waste Manager”, Bob Harrington is re-certifying for “Laser safety awareness” and a satellite accumulation area has been initiated for the facility. Signs warning of magnetic fields have been posted for those with pacemakers or other implants. The facility has been re-keyed and the appropriate personnel have been issued new building keys in order to maintain tighter security at the ATF.

1.   Next week ATF schedule: Please notices that, next week ATF routine maintenance is on Friday, not Monday.

2.   VISA alignment: Due to delay of the CO2 laser work, Don will be available for VISA alignment in the week of May 8.

3.   Vacuum interlock for the RF gun klystron: one of the possibility of QE degradation is the RF break down, we observed about 20% QE drop on Friday due to RF break down. Therefore, Mark will install vacuum interlock for the gun modulator.

4.   Linac water system: After finishing the vacuum interlock, Mark will continue work on the linac water system, and Bob will work on the plumbing.

5.   ATF control computer: ATF is in the process of upgrading the control system (both hardware and soft ware), but the present system will be the workhorse for near future. To reduce the burden of 130 MHz VAX, we will implement following login procedure immediately:

    A.  Use telnet to login at BNLATC.

    B.  Start Exceed or other X-window simulator.

    C.  Type atf at command line,  ATF control system will start, and follow usual routine to control             ATF system.

    D.  When finished, restore idle file. Close all X-window. And logout VAX

6.   ATF started enforcing the new BLOSA form for all users this week, and I want to thank all users for their cooperation on this matter. The persons qualified for delivering ATF BLOSA training are Bill Cahill, Marcus Babzien and X.J. Wang. A list of BLOSA certified users is at: http://nslsweb.nsls.bnl.gov/Training/atf-blosa.htm, which can be accessed from the ATF ES&H page.

7.   ATF operation:

A.  We did RF measurement of the gun on Monday. Both the field balance and the resonant frequency are correct within 10 KHz. We established that the gun temperature drift was due to the solenoid magnet. We tried to install a temporary temperature stabilized chiller for the solenoid without success (not enough power).  We spent more time developing a gun temperature stabilization procedure, and stabilized the klystron temperature by use of the heater exchanger.

B.  We did more studies on the laser imaging on the cathode. The profile of the laser on the cathode is quite different from what it was a couple of months ago. Marcus realigned the laser on the cathode, and a 200 micron horizontal error was observed.  Some non-uniformity of cathode surface visible, which could explain the QE drop we observed in the last couple weeks. We need more studies on the laser profile and spot size. We observed a space charge bunch lengthening effect at less than  2 nC (maximum).  We measured the beam energy out of gun, 4.3 MeV, which is where we have been operating.

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The FUA for the ATF identifies all hazards that are currently present in the building.  Once the FUA is available on SBMS (any day now), you will find that section 4 lists the hazards and references the standards or procedures that apply to controlling the hazard.  The list of hazards contains no surprises. You will find that it includes hazards like electrical, chemicals, cryogens, radiation, etc.  It lists all the hazards that we have worked with previously . 

What you need to know is the following: if a new hazard is identified in your work planning, we will need to conduct a special review to see if it can be safely performed and we will need to modify our FUA if we decide that we can do it.  As an example, work involving explosives or large quantities of nuclear material is not currently authorized for our building in our FUA.  Permission to use our facilities for that type of work would require special reviews and authorizations and result in a modification to our FUA.

Other than being sensitive to work involving new hazards, most people do not have need to use the FUA as other than a reference document. 

The ATF started enforcing the new BLOSA form for all users this week. There persons qualified for delivering ATF BLOSA training are W. Cahill, M.

Babzien and X.J. Wang. A list of BLOSA certified users is at:

http://nslsweb.nsls.bnl.gov/Training/atf-blosa.htm, which can be accessed from the ATF ES&H page.

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