Isaac Earle has recently been managing the fabrication of some new Be target cassettes for the T1 / T2 Meson Hall target ladders (WO 41527).

The machine shop has outsourced the cassette tubes to an external shop for wire EDM cutting, as it produces a much more repeatable and consistent wall thickness without the need for delicate forming and welding.

However, the legacy end-cap design TBP1690 calls out a thin-wall formed frame to help brace the window in place and provide material to fusion weld the rim of the end cap to the cassette tube.  The legacy design frame is extremely thin compared to the tube wall thickness, and this mismatch is extremely difficult to EB weld reliably.  If a mistake is made, the entire EDM cassette tube is scrapped.

Bob Welbourn and the machine shop have come up with an improved design for the frame and window with slightly modified forming tools.

The window thickness .003" and tube wall thickness .010" remain the same.  The only change is to the thickness of the welding frame, which is now matched with the tube wall thickness (previously .003", now .010").

Photos of the old (right) and new (left) weld results are attached, as well as the new forming tools created by Bob Welbourn.

The shop is now able to make a confident and reliable weld for the end caps.

I am not sure that the increased frame thickness will have any affect on the beam entry into the target cassette, but my assumption is that this region is not critical.  Now, if the beam does enter that material at the edge of the cap / tube, and the temperature changes during operation, there will be a more secure weld there due to this design improvement.

The machine shop was waiting for the OK to finish welding the end caps into the frames using this new technique / design, and seeing as how the old option was likely to produce more leaking or scrap parts, I gave them the go-ahead to proceed.

Isaac will take care of the drawing and documentation updates when he returns from holiday.

Thanks and regards,

Grant

The following work was performed on the T2-MK1 target.  The profile monitor and monitor cage on this target were damaged in January 2013, See E-Log #68

Oct 23:
- T2-MK1 target moved from storage pit hole #4 to the hot cell (field measurement was not possible because the pole monitor had issues
- Position 2 and 3 targets photographed (see attached)
- Position 3 target (10cm Be) removed.  This target had accumulated 11.5 months of beam time.  Maximum for T2 targets is 12 months according to new schedule.

Oct 26:
- Position 3 plugged
- Profile monitor cage inspected and photographed. The cage (TBP0106D) and aluminum frame (TBP0101C) were both noticeably damaged (see photos)
- Attempted to insert dummy cassette, went in smoothly
- Moved target ladder through all positions, moves smoothly, micro-switches ok, potentiometer ok
- Motor drive coupling inspected - no issues
- Actuated monitor in and out: traveled fairly smoothly, 40psi required to insert, 20psi to pull back out
- Dummy cassette removed, real replacement cassette inserted (went smoothly)
- Horizontal wires inspected w/ Nikon level, found to be crooked

Oct 27:
- Cassette frame nuts (TBP0108C-2) loosened and monitor frame adjusted until horizontal wires horizontal, nuts re-tightened and torqued
- Vertical and horizontal measurements of profile monitor position measured - All within 1-2mm of previous measurements in 2010
- Although some physical damage to frame is visible it still positions monitor in correct location and seems to be fully functional, therefore will use if electrical is ok

Oct 28:
- Electrical check performed on profile monitor by Mike Russell
- All 26 wires visible.  Screenshot of scope taken (see attached)
- Moved to position 5 to stretch bellows, and air left running through target overnight to dry

Oct 29:
- Cold trap filled with LN2, pumping with new leak detector started
- Test port at E-1 Torr range after 30s, E-2 after 1.5mins, E-3 range after 3mins, 0.0E-10 torrL/s leak rate after ~10mins, TP at <1.0E-3Torr after ~15mins
- Leak check performed with 3psi helium applied w/ ~0.5s bursts at all target locations, bellows, top of vac flange, and Hansen fittings
- Small leak found at left bellows lower weld (expect is negligible for water use), no response from all target locations (see attached scan of leak check notes), deemed water leak tight

Nov 3:
- Plumb bob measurements taken
- Vertical and horizontal measurements of Pos'n 2 target taken
- Target ladder moved to position 0, profile monitor secured in IN position to prevent damage during move

Nov 5:
- Target returned to storage pit hole #4
- Field of 53mSv/hr measured at ~0.3m (attempted 0.5m measurement, but was a little close)

The T2-MK1 target is now fully functional and ready for use.  The 10cm Be target in position 2 has not seen beam.

Note that the target window welds show some uneveness (see photos), but not expected to affect performance b/c leak tight.  The elevations sheet will be updated and filed in the T2 Binder in the Meson Hall HC Lab Office.

 The T1 and T2 targets were both moved from Position 0 to Position 4 at approximately 2:30am on Saturday October 10th using the portable control box.  Operations had tried to move the T1 target to position 4 using the old control system but for unknown reasons it would move to any position except position 4 and the portable control box had to be used.  The portable control box should continue to be used for T1 and T2 target moves until the new control system is installed in the 2016 shutdown.

When the damage to the T2 Protect Monitor was found to be caused by flying debris from a vacuum spike (see e-log #179), it was decided that the T1 Protect Monitor should also be replaced.

Oct 8:

- The T1-MK2 target was transported from the beam line to the hot cell after the T2 target was returned to the beamline (see e-log #180).  The T1 target was 38.9mSv/hr at 0.5m

- The T1 target was inspected in the hot cell: profile monitor looked ok, protect monitor damaged with holes and dents on upstream side (see attached photos), position 4 target looked ok with beam spots roughly centered (see photos)

- The old protect monitor was removed in the hot cell and a new monitor supplied by Probes Group was installed (previously undocumented brass spacers were seen over the monitor cassette alignment pins on the target)

- The T1-MK2 profile and protect monitors were checked by Probes Group at the hot cell --> both ok

- Measured elevation of the new T1-MK2 protect monitor: 1831.1mm on entrance side (previously 1831.0 --> ok)

- Position 4 target entrance side elevation checked: 1832.9mm (previously 1831.9mm --> 1mm discrepancy)

- Position 4 exit side elevation measured: 1832.4mm (previously 1832.1mm --> ok)

- Protect monitor exit side elevation measured: 1833.7mm (previously 1833.3 --> ok)

- T1-MK2 target returned to beamline at approximately 5pm, no problems

- Vacuum pumped down quickly and it was decided that a leak check would not be necessary

Oct 9:

- All target services attached

- T1 target moved to Position 0 using remote control box

- T1 package started, no change to T1 vacuum

- T1 profile monitor and protect monitor electronics checked by Probes Group from mezzannine --> both ok

- T1 motor drive cable conected to controller in 1A racks.  The T1 ladder can be moved from the 1A racks mimic panel (T2 still requires portable control box)

- Actuation of the T1 profile monitor was tested --> actuated properly, no change in vacuum

- T1 cooling package expansion tank level checked: no change

- The T1 area is ready to be covered

While the T2 monolith was uncovered for T2 Protect repair (see previous e-log), it was decided that the T2 target should be moved to the hot cell to address issues discovered last week with target ladder movement (see e-log #175)

Oct 7:

- T2-MK2 target was moved from the beamline to the hot cell after the T2 protect was reinstalled (the target measured 896mSv/hr at 0.5m)

- The target was inspected in the hot cell: profile monitor looked normal, two beam spots (one higher, one lower) were observed on the entrance window (see photos), the spot on the exit window was low but not quite touching the weld

- T2 profile monitor was checked by probes group at the hot cell --> ok

- Ladder movement was checked by cycling through all target positions twice using the portable control box.  This revealed that the drive motor is actually functioning properly and the fault lies elsewhere

- Tested T2 motor drive cable from 1A racks to beamline with Dave Cameron.  Found Pin B has 190kOhm short to building ground.  Attempts to fix the cable at both ends were unsuccessful and spare wires in the bundle could not be used because there is a break in the cable at an unknown location and use of wire colours in both sections is inconsistent

- Checked entrance side elevation: 1839.0mm with potentiometer at 16.19kOhms.  This is consistent with previous measurement of 1838.7mm.  This confirms that pot, motor, and drivetrain for ladder movement are all ok.

Oct 8:

- Decided to run new cable for target motor drive  (already had on hand for T1/T2 controls upgrade in 2016 shutdown).  The cable is labeled T2TGTMTR-DRV.  It was first tested at the hot cell and then installed by Doug and Ron

- The T2-MK2 target was returned to the beamline.  A camera and monitor setup was used to watch the target entering the hole remotely which greatly reduced dose  (inserting the target requires multiple iterations to get alignment correct, so dose is typically higher than when removing devices from the monolith)

- T2 profile and protect monitors checked by Probes Group from the mezannine --> both ok

- Pumping on T2 volume began late morning, leak was found at T2 protect flange (see previous e-log), after correcting this the vacuum pumped down normally.  A helium leak check was performed on all flanges on the T2 monolith --> no leaks found

Oct 9:

- All services attached to target

- T2-MK2 target moved to position 0 using the new cable and the portable control box

- T2 cooling package started (no change to vacuum)

- T2 cooling package expansion tank level checked - the tank was only ~1/3 full, suspected leak through disconnected female hansen connection.  Tank was refilled to normal level using ISIS water

- Plant Group began replacement of blocks over T2 late morning

On Monday Oct 5th a decision was made to uncover and remove the T2 Protect Monitor due to faulty readings.  The monitor had been behaving strangely since the September shutdown, and had been getting worse over time.

- Blocks were removed over T2 starting Monday afternoon.  It is necessary to remove the narrow 12' block and two 6' blocks west of the T2 plug block in order to fit the flask frame in for protect monitor removal

- The monitor was moved to the hot cell by 7pm on Monday.  Pierre was operating the crane and there were no issues with the move.  (monitor measured 15mSv/hr at 0.5m)

Oct 6:

- Monitor inspected: a thin piece of foil was found jammed into the entrance side of the monitor (see photos) & a heat or burn mark was seen on the exit side above and to the south of the plate gap.  It is suspected that this material traveled down the beamline at high speed when there was a vacuum burst during the September shutdown.  In light of this information it was decided to remove the T2 target and T1 target as well (see following e-logs)

- Monitor elevation measured: 1835.8mm (april 2015 measurement was 1836.1 --> ok)

- Old monitor cassette removed, new one installed.  Elevation checked: 1832.2mm - did not match, removed, decontaminated, and returned to Probes for adjustment

- Adjusted monitor installed, elevation checked: 1835.8mm --> ok

- Electrical check done by Probes group at hot cell: found left plate shorted to ground

- Cassette removed, decontaminated, and repaired by Probes Group

- Cassette reinstalled, and electrical check repeated --> ok

Oct 7:

- Monitor elevation re-checked: 1836.2mm --> ok

- T2 protect returned to beamline, bolts installed, cables connected

Oct 8:

- Vacuum pumped on T2 volume after T2-MK2 target returned (see next e-log):  Only reached 2 Torr and a leak was heard coming from T2 protect flange.

- T2 protect was unbolted and lifted ~1in for cleaning of the flange base and o-ring

- The T2 volume then pumped down normally

- A helium leak check of all flanges on the T2 monolith was done by Vacuum Group --> no leaks found

 The following instructions were provided by Graham Waters:

From diag5pc bootup

Password: cfzx29mkdr

Bring up a terminal (click on "terminal icon" left side of screen)
> su
> xpfk34yzjc
> chmod o+rw /dev/ttyS0
> chmod o+rw /dev/ttys1

Bring up terminal emulator GTKTerm
   From booton left of screen
  Click on Applications->Accessories->GTKTerm 

 The T2 protect monitor cassette removed in April 2015 (see E-log #154) was surveyed today.  It was approximately 3mSv/hr at 0.5m and 15mSv/hr on contact.  It is unlikely that this monitor will ever be cool enough for hands-on elevation adjustment that it requires, therefore it has been bagged, labeled, and transferred to the east hot cell for storage.  

Today the T1MK2 target was moved from Position 4 to Position 0 to lower the Rad fields for the 1AM7 repair in the 1A Tunnel. The Rad levels were still to high only dropping by 1000uSv/Hr to 5000uSv/Hr, so the 1AM7 repair is planned for next Tuesday's maintenance day on Oct 6th.  1A will be off till then giving a longer cool down. 

The target was then moved moved back to Position 4 with the Pot ratio reading 0.699. The target was moved using the portable Control box.  The "power on light" on the Control box needs to be replaced.

Note: The MS connector on the 1AT2 cable needs to be tighten before using.  It became loose when swapping the portable Control box cable to the 1AT1 cable.

The cooling package turned on ok after the vacuum was established.

Don Jackson assisted me with this operation and was appriciated....

 The stepper motor that drives the target ladder on T2-MK2 has failed.  This is the cause of the difficulty moving the target ladder yesterday afternoon (see previous e-log).  This was confirmed this morning by attempting to move the T1-MK1 target ladder in the storage pit using the portable control box - the ladder moved with no issues.

The motor is scheduled for replacement during the 2016 winter shutdown unless it is needed more urgently.  Operations have been informed that T2 ladder movement will not be possible until this motor is replaced.

The T1 and T2 targets were moved to position zero, then back to the target position today so that beam profile could be checked using the profile monitors.  Movement for both targets was done with the portable control box.

The T1 target was moved from Position 4 to Position 0, then back to Position 4 (after checking the profile) with no issues.

While moving the T2 target from Position 4 to Position 0 the ladder stopped moving part way through travel.  By toggling the control box "RUN / OFF" switch the motion could be restarted.  This had to be done 2 or 3 times to reach Position 0.  When returning to Position 4 after checking the profile the problem became more severe.  It took over 20 minutes to move from Position 0 to 4 because the ladder only moved slightly or not at all each time the switch was toggled.  This is either due to a failed motor on the target, or failure of the portable control box.

The next step will be to try moving the ladder of one of the target assemblies in the storage pit to determine which is at fault.  In the mean time neither the T1 nor T2 target ladder should be moved.

The warm cell water window tanks were filled on September 17 after 2 weeks of curing time.  A water leak was found coming from the seals of a plastic pipe joining the two tanks near the top.  This was repaired using rubber gaskets and quick cure caulking.  The tank was refilled on September 18 and no longer leaked from that location.  The sand filter was backflushed with the water exhausted to the grass area outside the hot cell lab until the water ran clear.  The pump was then started with the water circulating normally through the filter.  Small water leaks were observed coming from 3 of the 4 plastic ball valves on the filter loop piping.  These leaks stopped after approximately 3 days of continuous running, and are still leak tight now.

During this repair job it was observed that the support wheels for the warm cell manipulators are crumbling and should be replaced before the next time the manipulators are used.

 The RH hot cell lab active sump high level sensor was tested as part of the yearly scheduled inspection.  High water level was simulated by tilting the sensor sideways with a long pole sample scoop.  The Main Control Room and Hua Yang from Nuclear Medicine were notified before the test.  The alarm sounded as expected, and a message was received in the main control room.  This is a latching signal, so a Control Room operator will go to the MHESA RCR lab to reset the alarm.  The water level was approximately 12" below the high level sensor, so the sump may need to be sampled and emptied soon.

Since the previous E-Log the following tasks have been completed:

- Panel spacer rods installed at 4 locations in each tank (two top, two bottom at approximately 1/3 and 2/3 the way across)
- Spacer rods expanded only slightly to begin compressing the rubber window spacers while still leaving at least a 8mm gap between window and frame
- Window and frame around seal area masked off with masking tape
- Sealant was applied from the outside using a plastic cone tip with a copper tube attachment to allow sealant injection to the bottom of the sealant cavity.  The process involved having one person inside the tank to make sure the sealant cavity was completely filled with no voids. A total of 42 of the 20oz. sausages were required.  Two spare unopened sausages remain.

The sealant will now be left for 2 weeks to cure before water is added to the tank.

The following tasks were completed over the past 2 weeks:

- Aquarium Technology Ltd. (UK) was contacted regarding best method for replacing window seal.  A detailed procedure was provided (attached below)
- The warm cell windows were determined to be acrylic, not glass.  Estimated weight: 450lb per panel

- All water in the warm cell windows was released to grassy area outside the lab after approval from Gord Wood (OH&S) and Joe Mildenberger (RPG)
- Warm cell was cleaned up and blocks were configured to make fields as low as possible in the work area around the windows (~2micro Sv/hr max field around windows).  No contamination found on warm cell floor.
- The old seal around each window was cut mechanically with a thin blade
- The panel spacer rods were removed  (most were constructed of SS and Al, however a couple were mild steel and were badly corroded)
- The window panels were separated from the frame using a rubber mallet and moved to the center of the tank (the panels were not removed from the tanks for this repair)
- The old seal material was removed from the panels and the aluminum frame using WD40 or mineral spirits to help break it down (this was a very tedious and unpleasant task)
- Pitting due to corrosion was found in various places on the aluminum frame.  It appeared to be worst where mild steel spacer rods were used, and also worse at weld locations (see attached photo).  Max depth of pits ~1/8"
- The corrosion was cleaned as much as possible using a wire brush then rags with mineral spirits
- A final clean of sealing surfaces was done with isopropyl alcohol
- A deep pit (~1/4" deep) was found on the inside of the inside of the aluminum frame on the west tank, south window (see attached photo)
- This pit, as well as some other smaller ones on the same side were filled with Dow Corning 791 sealant material

- Rubber stand-offs (Digi-Key #SJ5009-0-ND) were installed on the frame side in the center of the sealing faces (3 top, 3 bottom)
- The panels were moved back into place resting on 3/8" thick aluminum spacers (see attached photo).  These replaced spacers of the same size and material that were slightly corroded

The following tasks remain to be completed:

- Install panel spacer rods (mild steel rods to be replaced with SS or Al)
- Apply sealant to all panels from outside the tank as detailed in the procedure using 20oz pneumatic applicator caulk gun (PO: TR206556)
- Install corrosion inhibiting pads inside tank.  Will use 6 pads per tank, (4x McMaster 3609K2 & 2x McMaster 3590K2 per tank)
- Perform final clean of inside of windows and tank
- After 14 days cure time fill tanks with city water and allow to sit to check for leaks
- If leak tight, use water in tanks to back-flush the sand filter
- Refill tanks and start pump with filter in normal mode
- Occasionally check for water leaks and check status of pitting inside tank over the coming months/years
- Also monitor corrosion inhibiting pads and replace or change materials if necessary

Summarized Seal Replacement Procedure provided by Aquarium Technology Ltd:

1) Cut out the viewing panel entirely and mechanically clean all sealant traces from both the panel and the frame bearing faces of the tank structure

2) Degrease all sealing surfaces with something like pure petroleum spirit (mineral spirit) which won't harm the acrylic

3) Reinstall the clean viewing panel spacing it off the frame bearing face by around 10mm using self adhesive rubber stand-offs  (depending on panel flatness likely no more than 3 needed along the top and bottom)

4) Brace the panel in place, mask off the frame and panel, and then inject Dow Corning 791 sealant from the outside.  Ensure that the sealant goes in under pressure, fully wets both surfaces, and completely fills the void.

5) Allow the sealant to cure for 10-14 days before filling the tanks

The 4" Marman flange clamp (IRH0001) labeled "Clamp A",  as used in the testing detailed in Document-114623 Release 1, has been disassembled.  The parts were used to build a TRH1257 clamp which uses the new TRH1259 jaw with 0.480" jaw root width.  This new clamp has been labeled "TRH1257-#01", and will be tested with Helicoflex H-303654 seals in the near future.

T1 and T2 beryllium target failure history was investigated back to 2000 (as far as XSTRIP records were readily available).  For each target cassette the following were noted: length of time the target was subject to direct beam, length of time the target was on the ladder w/o direct beam, and method of failure.  The purpose of the study was to devise a target replacement strategy so that T1 and T2 beryllium targets are preemptively retired from service to reduce the occurrence of failure while running which causes loss of beam time, extra dose to personnel, and damage to equipment.

The following recommendations are the result of the study:
- T1 beryllium targets should be retired after 9.0 months of running time
- T2 beryllium targets should be retired after 12.0 months of running time
- Multiple targets should be installed on each target ladder (at least 2, possibly 3) so that targets may be switched during a running period if required and less target assembly moves are required

A PDF copy of the Excel spreadsheet is attached which includes target use history, failure history, summary of results, and more specific recommendations for each target assembly.  This study and the replacement plan recommendations were reviewed and endorsed by Grant Minor and Yuri Bylinski.  This spreadsheet should be reviewed and updated every shutdown period (including Fall mini-shutdowns), as well as anytime there is a target failure.

- All T1 and T2 values on XTPAGE were stripped back to April 1, 2015:  All systems appear to be functioning normally, nothing unusual observed

- Expansion tank levels checked visually:  T1 level at 1/2" above top sensor nut, T2 level at 1/4" below top sensor nut --> filled to 1/2" above

- Lower air amplifier in use; cool to touch; approximately 25s between each cycle (when air is exhausted from device)

An order for new T1 and T2  beryllium targets was submitted to the TRIUMF machine shop today.  A total of seven T2 targets and twleve T1 targets were ordered to match existing stock of wire EDM target shells.  All required materials were supplied.  Completion by October 30, 2015 was requested.
 

A complete set of new drawings for both targets were released in June 2015 (TBP1683 for 12mm T1 Be target; TBP1691 for 10cm T2 Be target)

Current target stock for T1 (12mm Be) includes: 1 target on the shelf, 1 target on the MK1 target assembly (position 4, has not seen beam), 1 target on the MK2 target assembly (position 4, currently in use).

Current target stock for T2 (10cm Be) includes: 1 target on the shelf, 2 targets on the MK1 target assembly (position 3, has seen beam;  position 2 has not seen beam), 1 target on the MK2 target assembly (position 4, currently in use).

 A 5lb roll of 347SS sheet was received today.  This alloy is to be used for the target windows of the new T1 and T2 beryllium target cassettes that will be manufactured in the near future.  The material was ordered from Alloys International (PO# TR206407).  A mill spec report was included with the material, a scanned copy is attached in PDF format.  The roll will be stored in the meson hall RH hot cell lab office on the shelving above the work bench.