Notes of most important TASKS, events AND problems in the laboratory

(Ervin Racz)

1) October 1, 2009: ASE pinhole damage

a. Beam profile after spatial filter pinhole was bad.

b. ASE spatial filter pinhole quality was checked.

c. Pinhole was totally damaged. Circle spot became elliptical.

d. Pinhole was changed; new fused silica pinhole with 270 μm diameter was installed.

e. Observation video camera was installed. Reason: checking beam position on the ASE spatial filter pinhole.

2) October 6, 2009: Pockel’s cell signal drop

a. Decreased amplitude of the envelope of the Hurricane Pockel’s cell signal was observed on the oscilloscope. Amplitude was about half size as before (~400 mV signal).

b. Same time very low - ~ 5mW – UV power was measured after Tripler box. Usual UV power is ~45-50 mW after Tripler box.

c. Significantly higher room temperature was measured from September 30, 2009. Room temperature was changed from 68 F to 73-74 F.

d. Pockel’s cell signal was slowly decreasing from September 30 to October 6.

e. Suspicion: reason may be:

i. – modified room temperature

ii. – decreasing of the power of Evolution pump laser

f. Without touching anything Pockel’s cell signal became good again next day. Hurricane was working fine on October 7 and 8.

g. Longer observation is suggested.

3) October 7, 2009: Fixing MaIN water system leak

a. Some valves at main water system were leaking. Reason: Old or bad quality o-rings at valves.

b. Plumbers started to work on water system. 4 old valves were changed. New ball-valves were installed.

c. Replacement of main valve and install one more flow filter are necessary.

d. After we bought filter plumber work will be done.

4) OCTOBER 12, 2009: PROMETHEUS CATHODE VOLTAGE PROBLEM

a. We have noticed for the past several runs that the amplitude and plot of the cathode voltage (on the oscilloscope screen) seems to change shot to shot.

b. The cathode voltage went to zero sometimes (voltage meter at the blue box).

c. The sounds of the Prometheus discharges were also changed.

d. We wrote e-mail to Randy about this problem. We are waiting for the answer.

Normal cathode plot (blue curve) Cathode plot with low amplitude

e. Possible reason: one resistor at the cathode blue box is damaged (burned connection) and it was not connected to the system. Cathode discharges may instable.

f. We are buying a new resistor.

g. After several days test run and discussion with Randy we observed that the source of the unstable operation is the spark gap box at pre-ionizer.

h. A sharp edge nut was replaced to a smoother one in spark gap box.

i. After installed new nut Prometheus operation looks stable.

5) October 15, 2009: FRONT END LAPTOP DAMAGE

a. On October 14 the front end laptop stopped with “blue screen die” effect twice on same day. Same “blue screen die” effect happened three times on October 15. Same time Mai Tai operation is also stopped.

b. Craig Pellegrini has started to fix the laptop problem. There is no laser this moment.

c. Laptop is damaged (hard disk and DVD ROM are damaged).

d. Craig Pellegrini bought new hard disc and he is fixing the problem at the laptop.

6) October 15, 2009: GUIDING GREEN LASER PROBLEM

a. I read an error message on LCD screen of the Innova 300 Ar-ion laser driver electronics: “Low I, laser will turn off in 3 hours”.

b. Voltage, current and Ar gas fill were checked. U=174.4 V at I=30 A was observed. This voltage is low. Ar gas fill is needed.

c. In order to build a gas balance autofill process was started at 38A. Voltage reached level of 197.4 V during an hour. Laser stopped fully.

d. Laser operation at normal current (20A) will be tested tomorrow. Hopefully, problem is fixed.

7) October 27, 2009: replacement of 3 mirror mounts at the front end

a. Sometimes strong beam line misalignment was observed behind focusing beam telescope. Possible reason for the alignment is the “mirror-trio” (a turning mirror and a beam periscope) behind tripler box.

b. The first small size turning mirror and the first mirror periscope behind tripler box was looking unstable.

c. A very rigid and stable mirror mount system was designed and made to hold all three mirrors stable together.

d. The new mirror mount system was installed on October 27, 2009.

e. After 2-3 days laser system use, the new mount is looking much stable than the original version.

(a) Old mirror mount system behind tripler box (b) New mirror mount system behind tripler box

8) NOVEMBER 9, 2009: SPARK GAP CLEANING AT 40168 MAXWELL TRIGGER GENERATOR AT PROMETHEUS

a. Prometheus operation was unstable. Every second shot misfired.

b. Trigger coming from 40168 Maxwell Trigger generator box was strongly jittering.

c. Spark gap in 40168 Maxwell Trigger Generator box was checked. Usual burned structure was observed with small carbon layer.

d. Spark gap was cleaned and installed.

e. After spark gap cleaning Prometheus operation was seemed to be stable.

9) DECEMBER – JANUARY FULL STOP WITH WHOLE LASER SYSTEM

a. Whole laser system was stopped in December and January. Stop was in progress between December 1, 2009 and January 31, 2010.

YEAR 2010

10) FEBRUARY 1, 2010: HURRICANE OUTPUT ENERY IS LOW

a. After restarting Hurricane laser system very low output energy was realized. UV (tripled) beam power was measured as 18-20 mW instead of 50-55 mW; and Mai Tai power was measured as ~730 mW instead of 840 mW.

b. On February 3-4 David Virgillito visited us in order to fix problems and make new alignment at Hurricane system.

c. During mapping status of the system a small wavelength shift on the Mai Tai pulse and incorrect Pockel’s cells operations were observed.

d. Mai Tai wavelength was corrected and set to 744 nm.

e. It was measured 20-23 % energy loss on each Pockel’s cell. (Pockel’s cells were bought in January, 2009.) Incorrect Pockel’s cell operation (huge loss in energy) is not normal after 1 year. New Pockel’s cells were bought from Spectra-Physics.

f. New Pockel’s cells were installed into the system on February 4, 2010.

g. After new alignment Hurricane output energy is lower than before…. We are working on to figure out possible reasons…

11) February: Very hot laboratory room temperature

a. In February very hot laboratory room temperature was measured many times. Temperature monitor showed 77-80 F number many times.

b. Due too hot temperature Hurricane laser system misaligned many times.

c. Decreasing room temperature to 68 F is necessary.

d. Physical Plant engineer decreased cold water temperature at heat exchanger in the basement. After several hours laboratory room temperature became lower.

e. Temperature is normalized on February 19.

f. Hurricane shows more stable operation than before.

12) FEBRUARY 24, 2010: PINHOLE MISALIGNMENT PROBLEM

a. ASE pinhole position misaligned many times during a day.

b. We observed that keeping the operating voltage on the stepper motors there is no pinhole misalignment.

c. Stepper motor driver box and power supply is cooled by a fan.

d. It seems problem is solved keeping voltage on the motors continuously.

13) MARCH 2010: PINHOLE OR BEAM MISALIGNMENT PROBLEM

a. Pinhole misaligned almost every day afternoon (randomly).

b. In order to check mirror mount stability, some test experiments were running last week in March.

c. Seed beam reflected far to check beam stability or mirror mount stability. Beam was moving downward during the test runs. It means that mirror mounts or the mechanical system not stable enough, mirrors can not keep beam in position.

d. Mirror mounts stability – independently from the small optical breadboard – was checked by the green guide laser at the big optical table. Mirror mounts looked stable. Reflected green laser pointing was stable during 3 days.

e. On March 31, 2010 4 pieces of new, more rigid and heavy duty mirror mounts were installed in front of ASE spatial filter pinholes. 4 LLG mirror mounts were replaced by the new mounts on both small optical breadboards. Hopefully, the new mounts will be more stable.

f. Summarizing observations it seems that mirror mounts are OK but the small optical breadboards are not stable enough to hold mirror mounts.

g. In order to stabilize small (2 x 3 feet) optical breadboards more, 2 x 2 new table legs were designed, made and installed to the tables. Stability test is in progress.

14) APRIL 1-2, 2010: LABORATORY ROOM TEMPERATURE IS VERY HOT

a. Laboratory room temperature was measured as 78 – 80 F. Outside temperature is also warm; it is around 74-80 F.

b. Physical Plants was informed about the problem.

c. Physical Plants investigation: a huge main valve at the air conditioner system in the basement was damaged. Fixing problem is in progress. During fixing main valve problem the entire SES building can not be air conditioned. Room temperature will be hot everywhere.

d. After fixing main valve problem Physical Plant will change the system from Winter-mode to Summer-mode. Building will be cooled and not warmed.

e. On April 2, 2010 laser system is not used until room temperature is not normalized. (On April 1, 2010 Hurricane and full system was used for experiment, but Hurricane was very unstable.)

Last modification: April 3, 2010.

Ervin Racz