2016-Mar-20 Diagnostic Development Biweekly Report

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  • Bunched beam controls
  • Worksheet for Harp position
  • GTS viewers & nomenclature


  • 1C12
  • DPIT


  • SCAM Requirements (MIZAR)
  • Quad resistance anomalies
  • M56 cavity - ops interface
  • C100 data handling & SEL/GRD transition
  • Cold start-up draft procedure

Chris: Waveguide layout for UITF 1C12

Joe Gubeli: The bulk of my time in the last two weeks was spent on incorporating the video acquisition system for the LDRDS into the WS machine. This is done for the local machine. Mike sent me an email with the unused slots on the remote machine. I will need to get an interface card for that. I did try to run the WS without luck. I’m not sure if something was damaged in transport or if the motor is incorrect. I did rewire the motor test fixture and the limit switches now work. I can read back the viewer positions but can’t get the solenoids to change. I will revert to the old controller to try to narrow down the problem. I also spent some time on 1C12 with Chris. Other than a missing flipper mirror, I believe it is on backlog, we have all the commercial HW. The MS parts are due next week. The three of us will need to sit down and discuss how to remotely control the filter wheel and flipper mirror. The power interface for the camera will also need to be agreed on. We had a DPIT meeting last week and I spent a little time on that.

Mike Tiefenback :

I had been anticipating coverage of Hall B on the weekends and setup on Friday pm into Sat am, but those didn't happen due to CHL issues. Therefore I took the opportunity to dive into the diagnostic pool.

The diagnostic PIT seems to be moving along, and I was there Wednesday. I'm attempting to answer some questions Roger Flood has about the SCAM requirements for the Mizar pulser functionality, but I'm not confident that I understand exactly in what detail he's asking. We'll get that settled.

I have tracked some magnet issues, monitoring resistances and have some outliers I am questioning. I'll be having those examined during our forced downtime. QA's for instance, ought to have a well-defined resistance in the lab. I'd been told variously 2.5/2.7 ohms, but leads add to that. There are magnets in the system for which the computed resistance is 2.5 ohms or less for the magnet plus leads, and that raises questions for me. Many of the QAs have total resistances between 3.0 and 3.3 ohms, but these may be due to long, narrow-gauge leads. This is easier to believe than 2.5 ohms, but I'll follow it up. There are also some in-the-air questions about definitions of multiple magnet layout on a common bus -- how to handle, how to report, what ced should say, how deep to go in description. I need to have these settled in an intuitive way to avoid operator confusion. All operator confusion results in lost clock time while the hair roots are massaged.

The M56 cavity interface (time of arrival cavities; Yao[-ish] cavities) needs polishing, and I've been providing an updated data processing flow to Michael Johnson. I provided some mock data streams for him to test, plus an implementation of an algorithm that does what I think should happen. A working version should be available for test quite soon, and _may_ be up and running on-line in the MCC for our restoration of beam next week. I'd like that. I also spend time conferring with the operators on such interface issues. They live with operational interfaces, and I want to get their opinions on workability and intuitive-ness prior to fielding changes in their tools. This is both courteous and targeted at morale/efficiency. Having operations staff buy-in makes it more likely that the tool will not be misconfigured or misused. Both mistakes happen.

The B-team has requested a tutorial on multipass steering issues, what we know, how we know it, what open questions remain, and how are we gonna answer them. I'm working in that, and the info is relevant to the JLab/BNL collaboration on a 5-pass ERL demo.

I'm hoping to get a with-beam calibration of the M56 cavity sensor time-of-flight through all four quadrants of relative phase, and use this at the time of that calibration to measure some accelerating gradients with that system. This is entirely different from our normal spectrometer-based energy gain measurements and can prospectively provide us with a missing element: a linearity check for GSET vs. acceleration. I have reviewed and revised the ATLis test plan for this and made preparations for fielding the test.

I also conferred with Trent Allison on the C100 data handling and have made some suggestions to him about ways to smooth the high-gradient transition from SEL mode to GDR mode. His observations on a phase offset shift between the two modes of operation were interesting, and I suggested how he might test the mechanism. The initial impressions he (and others) had generated focused on the SEL mode being in an ill-defined fashion "different" from the GDR mode due to the SEL mode being targeted at driving the cavity to peak gradient and the GDR mode being a "stand and deliver" mode to hold fixed gradient/phase. This seemed an unreasonable perspective to me, and I suggested it was more likely that a phase shift would be due to different data paths taken inside the module -- more steps in the pipeline possibly resulting in a phase shift. There appears to be a way to configure the SEL mode operation to use the same pipeline as the GDR mode, and if that results in no shift in relative phase between SEL/GDR, then one nagging question will have been resolved. This issue does have some small effect how they do SEL/GDR transitions in the C100s.

I also drafted a procedure for cold start-up of a linac, including no-knowledge-assumed phasing of the cavities using the M56 cavity signal. This is a substitute for the beam loading signal we no longer have available in the control room. I traced some problems in installation/powering of CE correctors for the Hall C Compton polarimeter and possibly prevented over-stressing of some of the hardware. I tried to bring clarity to testing of the 3-way A/B/C 5-pass beam split by pointing out what was critical and what wasn't. I brought some of our DC power folks up to speed on internal diagnostics of the trim magnet system (flicker/noise alarm features as flags for loose terminals). I think I headed off unnecessary time being spent on the questions of GMES drift in the linacs over the spring run. And I even filled out my time sheet.