CESR Tuning and Measurements - Attempted to observe the longitudinal dipole coupled bunch instability threshold for 9t.2b in different spacings. (Current limited by vacuum chamber heating and W RF ion gauge trips). Single and two beam thresholds are higher now than they were in November of 1998. S

A quick attempt at a crossing point measurement indicated that bunches were not even close to crossing at the center of the 0E/W BPMs. The shift in the null from east to west was about 85MHz, implying a 30mm shift in the position of the crossing point. Using the program TRIG, it was noticed that with T1B1 of both positrons and electrons in CESR, the bunches were offset from each other by a 2ns bucket. In the interest of getting the bunches to line up on the Sampling Scope (CRB.02) timing marker, I first changed the injection phase in positron conditions from -48 to +147 (adding 195 which is a 2ns bucket per REM). This put both the electrons and the positrons on the timing marker once electrons were injected. ANYWAY, at this point, the CSR RF PHASE has been set so that the bunches will collide at the IP. This was confirmed by a crossing point measurement. T

Safety - Added 2" high density poly along tunnel shielding wall just inside West Flare door. 4" poly added upstream of A cave along tunnel shielding wall. M

A residual radiation survey of the Q10W quad was done. The level today is 4.0mR/hr, April 12, 1999 level was 18.0mR/hr. W

Accelerator Cooling - e- injection in presence of e+: Only filled to 2ma/bunch in 4 bunches due to heating of sliding joint at 10west when we go to e- injection conditions (pr on etc.). Q

Checked cooling at Q10W and found the area a mess. Disconnected and re-dressed hose in that area. I thought that there may be a flow problem in one of the cooling loops but in the end I am not sure. We re-connected water and added a new cooling band at the sliding joint. Found flow through the cooling bands to be .5 GPM. Also checked flow through the north kicker flange and found it to be .5 GPM also. Still have heating problem in e- conditions. F

Inspected the 10W sliding joint chamber - all water appears to be connected and the time constant appears to be reasonably fast indicating a good path to cooling water. There was no OBVIOUS misalignment but we should check again on Monday. A calculation with nominal pretzel orbit in the wiggler (+11mm, +0.52 mr) suggests that power density on a uniform wall in this area would be around 0.25 kW/m at 250 mA positron beam current. S

The horizontal alignment of the vacuum chamber between the feedback kicker and Q10W was checked this morning. It was generally within +/- 1/16" of the centerline between Q09W and Q10W. After consulting a drawing of the chambers around this flange, we conclude that roughly 30 watts (at 250 mA e+ current) is hitting on the tip of the chamber just West of the oval flange. This is the power (roughly 1/3 W/mm @amp; 250 mA) that would have hit a uniform wall 45 mm from the beam centerline in the 97 mm recessed space around the oval flange. This may be the same condition as before the shutdown since this exact present CSR TC MON 50 location was not monitored. Considering the remoteness of cooling from this surface, the temperature rise may be reasonable. The solution is more cooling or possibly a water-cooled gasket-mask in the oval flange. M

Worked on the cooling band at 10W to get better contact. (I think we made some improvement) Added a cooling tube in the hole at 10W sliding joint. This is not as good as a cooling band BUT there was not room for this second cooling band. M

CSR TC MON #50 temperature went down about 6 °C at about 2 pm yesterday and is now totally indifferent to beam current and position. tc had pulled loose and was hanging in air; re kaptoned and clamped. T

Added a cooling band on the north flange (10" flange) of the north kicker at 10W. W

Vacuum - Found a very high pressure rise in at B3E, Q3E and SB3E when the stored beam got dumped this morning. The preesure did recover, but decide to leak check the region anyway. Found a relative big leak at the oval gasket bewteen the Q3E GV and B3E flange (He level @5e-9 amp). The leak was located on the wall side of the gasket. Tightened the gasket. Further leak check OK. F

Control System - Console problems: While tuning, the magnet clock hung. While resetting, console died. Restarted console, and the clock hung again and console died again. Restarted, tried a scalar to command. Console died again and slowed down cesr 25. From home, sbp restarted all programs, did a database refresh and moved dscope to the 29. Everything now appears to work fine. S

Linac RF - Observed many Thyratron 6 current trips, which are of two types:

1. When Klystron arcs, the Pulse (and Thyratron) current pulse gets very large as the Klystron voltage shorts out to zero.

2. Even with no Thyratron trigger board power (and thus no trigger) the Thyratron sometimes breaks down at random times (not when the other thyratrons fire). So with the trigger, one then gets too many Thyratron current pulses (of normal size).

The trip rate improved significantly after lowering the voltage and rep rate for a while, and then slowly increasing both to the usual values.

Note that we are now running Klystron 6 voltage about 16% higher than before the down period, but still below the normal operating point for this type of tube. But it is an old Klystron - rebuilt in 1971. Hopefully, the Klystron just needed some HV processing. Q

Later, had constant shunt doide trips. Found new Maxwell .008uF 50KV capacitor split down the middle. Replaced. Q

Disconnected HV to Linac Modulator 6, because of concerns of the Klystron arcing and the new capacitors failing. Will install additional insulation around capacitors and then try HV on the Klystron later.

In the meantime, the Linac must be tuned up without section 6. F

Retuned the PFN of modulator 6 to lower the high voltage on the klystron. The voltage was reduced from 237 KV to 220.8 KV.  S

The voltage on the klystron was increased by 5 KV to 225.8 KV. M

Previously, noticed that the Current signal for Thyratron 2 was a factor of two too large (had changed the trip level to compensate). Replaced Pearson current transformer (0.025 V/A) and adjusted voltage divider on Linac Fault Processor card so now have the right size signal for the interlock and the control room monitor respectively. M

Synchrotron RF - L5 tripped off on filament not ready. Read about 24 VAC, 11 A, so probably ok. Lowered the lower set point on the filament current action pack to get a reset. M

Feedback - Adjusted e- horz timings and turns delay for new Digital Signal Processors. Damping times are not

spectacular (~2 ms). Q

Adjusted e+ horizontal input timing (added noise suppression to button signal), output timing, turns delay and current calibration. F

Adjusted e- Horz input timing and e- Horz Feedback Gain after replacing front end card for inside button. F

Current monitor does not reliably indicate bunch current. Inadvertently fill to high single single bunch currents and there are warnings of high temperatures on 45e and 45w separator transitions. E- bunch current readout began to exhibit large errors. Symptoms are bunch 1 current limits at 6.5 mA and an bunch 2 current reads 4.5 mA. Tried resetting the e- horizontal digital signal processor (DSP) to no avail. Finally added 6 dB attenuators to the inside and outside button signal inputs and rescaled the e- current. S

Horz feedback does not seem to be working properly, 4th bunch is not getting damped very well. S

When changing the CSR RF PHASE the measured positron bunch current fell by about 0.5mA (out of 7mA) when changing from e+ to e- injection conditions. The effect was due to the fact that the positron horizontal feedback input timing (the source of the bunch current measurement) did not quite track the CSR RF PHASE. This effect seems to depend upon the value of CSR RF PHASE. Later on, it was noticed that the input timing that maximized the current with a single bunch was about 20cu different from the maximum with 9x2 positrons (1,3). T

CESR Magnets - vert steering at 9east is off and will not reset, chopper replaced Q-F

HB6 chopper replaced. S

Hardbend trim 4/5 East chopper blew agai.. Lifetimes in electron injection unacceptable. replacing.  M

CESR RF - Results of the reative cavity position measurements are:

W1-E2 2.79 mm (was -3.95 mm for W1 5-cell cavity)

W1-E1 7.91 mm (was 1.29 mm for W1 5-cell cavity)

E2-E1 5.13 mm (was 5.24 mm before shutdown)

One can see that W1 cavity has position error of 6.7 mm relative to its predecessor. As a result of this, the IP moved by 6.6 mm to the East. Also, there are still big RF phase errors which have to be fixed by adjusting tuning angles and East-West phase:

W1-E2 18.92 deg. (phase adjustment required)

W1-E1 29.83 deg. (phase adjustment required)

E2-E1 10.91 deg. (tuningle angle adjustment required)

These big errors result in large variations in beam loading among the cavities. At this point E1 cavity is loaded stronger than E2, and E2 is loaded stronger than W1. Q

The RF has been tripping off due to oscillations in W1 Hex Gas Flow. Adjusted the control loop parameters to stabilize the flow rate. Q LHe level in ALL three cryostata began to fall down. At the same time the level in the 2000 L dewar started to climb up. All instruments and control loops were working OK, and at about 2:00 AM situation reveresed and the cryostats He level began to rise. The most probable cause of this accident is a clogged cryoline between the 2000 L dewar and Mezannine valve box. Q

W1 HEX GAS FLOW: Found crossed control signal wires in a ribbon connector, remade connectror and control loop stabilized, briefly. Decided to replace mass flow valve and this has solved the instability problem. Wiring errors caused the flow oscillations in turn causing the valve to temperature cycle beyond design limitations. So the valve was HEXed by the crooked connector. F

Adjusted W1 phase regulator, was at limits. Still has the behavior of jumping from one operating point to another after a trip (I don't think it is the cause of the trip, but that has to be looked at). Moved the home position to close to the upper limit, since it wants to jump to the lower operating point, which is now slightly above the lower limit. We didn't see this with the copper cavities, so it may be due to signal level and/or cavity bandwidth changes affecting the loop dynamics. Haven't tried setting the home position close to the lower limit yet. F

Added a bandpass filter to the W1 cavity field signal amplifier, also removed a circulator. Adjusted the field attenuation, tuning angle and phase trombones to compensate. This necessitated adjustment of the west RF cavity field command and the west cavity phase. T