BLTWG Meeting 1/18/2008

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  • Time: 9:00 EST
  • Place: EVO and ESNET
  • Present: Ken Livingston, Yang Guangliang, Richard Jones, Elke Aschenauer, Tim Whitlatch, Elton Smith.


  1. Review Tim's interface drawings
  2. Review answers to vendors' questions
  3. Interface with accelerator

Tagger Interface Specification

  1. Qradrupole inner clearance: The tagger specification states that the clearance hole through the field region of the tagger quadrupole is of diameter 30 ± 2 mm. This leaves unspecified the inner diameter of the beam pipe. Jay Benesch wrote that:
    The quads in the hall D line will have 1.375" OD, 1.25" ID beam pipes. The tagger quad beam pipe should be as close to this as possible.
    This is useful guidance. Yang confirms that the field strength of these beamline quads would be sufficient for the tagger quad as well. Adopting that design would make spec'ing the tagger quadrupole very easy. An ID of 1.25" is 31.25 mm, within the specified tolerances. In the tagger simulation, Richard used 30mm for the inner diameter of the vacuum pipe between the radiator and the tagger vacuum box. Tim will communicate with Mark Wiseman and see if there are any drawbacks to our adopting the design of the beamline quadrupoles for the tagger quadrupole.
  2. Thin vacuum box exit window: The tagger specification does simply states that the exit window should be composed of aluminum and be "thin". It was suggested at the meeting that other materials, eg. kapton, aluminized mylar, or carbon fiber sheet might be alternatives to aluminum with greater strength per gram. Richard used a window thickness of 1mm of aluminum in the simulation, without any apparent degradation in the performance of the hodoscopes coming from radiation in the window. The consensus of those present was that 1mm is thicker than we need, even if aluminum is chosen. Richard will contact Dan Sober and Franz Klein to ask what considerations should drive this choice.Franz: the exit windows (beam exit and long hodoscope exit) should be welded to the frame, thus stainless steel (1mil) or aluminum (5mil), both leading to an energy resolution error of about 0.015% in the hodoscopes. Other materials could be considered but require large flanges and o-rings.
  3. Tagger vacuum box downstream exit region: There is currently a thick flange with a lot of material producing interactions close to the tagging hodoscopes in the interface design. It has been suggested to replace this flange with a rectangular window with a large horizontal extent. Richard looked up what was used in that region in the simulation:
    The tagger simulation included a rectangular extension to the downstream end of the tagger vacuum box. It had inner dimensions of 8cm x 4cm and extended 280cm from the downstream end of the vacuum box proper. The rectangular pipe was not constructed symmetrically about the nominal electron beam path. Instead, the full-energy electron beam component is aligned 2cm from 3 of the 4 walls of the rectangular pipe, while the fourth wall (low-energy side of the electron beam) is 6cm from the beam and only 1mm (stainless steel) thick.
    An exit flange consistent with this design would have a rectangular opening 8cm wide x 4cm high, positioned so that the nominal electron beam passes through the center of a 4cm x 4cm square occupying the half of that opening on the small-deflection side.
  4. Richard suggested that a helium bag might be used in the region between the tagger vacuum box exit and the first electron beam dump shielding wall instead of a vacuum pipe. Tim will raise this question with the accelerator group and Radcon to see if such an idea is plausible. Franz: The primary beam exit can be much improved compared to the current Hall-B solution using carbon fiber (or rectangular pipe with thin foil on the upper part of the small-deflection side). This requires some simulation and optimization.

Vendor's Questions

So far we are only aware of one firm interested in the contract. The closing date is presently January 31. One bidder’s questions (black) and answers from Tim (red) are listed below.

  1. Will JSA provide all supporting data, specifically calculations, developed by University of Glasgow to arrive at the 35% level concept design?
  2. If University of Glasgow (UoG) is used for magnetic field calculations as offered in the Statement of Work, how is UoG funded, what is the contractual relation of contractor, JSA and UoG?
      JSA will hold the only contract with the successful bidder. JSA already has a contract in place with UoG.
  3. How will the contractor be insulated from potentially unacceptable cost and/or schedule performance of UoG?
      The work from UoG will be through JSA and will not add additional cost to the contractor. Schedule performance issue from UoG will be the responsibility of JSA.
  4. How will JSA evaluate bids given that the use of UoG is offered as an option – use of UoG funded by JSA is not equivalent to a contractor doing the work internally?
      Total cost of the contractors bid will be one of the considerations. Since UoG services are essentially free to the contractor, it may affect the final award.
  5. If UoG is to be funded by the contractor, how are bids obtained and can UoG provide a bid in time to support the 1/16/08 submittal date?
      No bids are required from UoG. JSA will be responsible for this.
  6. How will JSA handle ITAR issues and approvals for data to be shared between the contractor and UoG?
      This will occur through the JSA-Contractor contract.
  7. The component sizes and connection details in the concept must be based on some preliminary material specifications and calculations. Will those material selections and associated design criteria be provided?
      JSA will supply the preliminary material, design reports and an interface drawing showing the major interfaces.
  8. Are there concept drawings for the vacuum chamber ports/windows and will those be provided (assume the “vacuum box” is the combination of pole shoes and yokes as shown on assembly drawing 9086-02-00-00-AD provided on the JSA procurement web site; there is no separate box structure).
      JSA will supply a 3D AutoCad model of the concept.
  9. The Statement of Work states that “a finite element analysis must be performed for all parts that are subject to strong forces.” However, the Stage 2 work description specifically calls for FEA of the energized magnet and of the vacuum box rib structure. What is JSA’s definition of “strong forces?” Are the two stated FEA requirements the minimum level of FEA required?
      Magnetic forces, Vacuum loads and weight are the “strong forces”.
  10. For vacuum box analysis purposes, is the contractor to assume that a complete vacuum is achieved?
      Yes, 1e-5 Torr vacuum with leak rates less than 3 e-9 too-liter/sec max.
  11. Are there any building code requirements for any of the components in addition to the operational technical specifications provided? If so, what are they?
      Not for the magnet itself. The base will need to be secured to the concrete floor and shown on the interface drawing.
  12. What are the acceptable stress levels for the various components (what design safety factors does JSA require)?
      We generally use a factor of 4 to the ultimate strength.
  13. What are the acceptable deflection criteria, if any?
      Deflections of 0.2mm in the pole gaps are acceptable. Vacuum chamber deflections on the order of 2mm are acceptable as stated in the specification.
  14. What are the design characteristics of the building and/or structure that this project connects to?
      Concrete walls and floor. The floors are designed to take any of the loads from the weight of the Tagger. See the interface drawing.
  15. Are existing UoG concept drawings available as a 3-D model and in what format (is the format compatible with AutoDesk “Inventor” software)?
      A 3D AutoCad model will be supplied.
  16. The RFQ requests the resumes of Designers that the contractor proposes to use, but does not specify these as “key personnel.” Clause JSA-112 addresses key personnel and the contractor’s ability to adjust personnel with Subcontracting Officer notification/approval/concurrence. Please clarify if Designers are considered key personnel for both resume submittal and workforce planning purposes. Contractor respectfully requests that designers not be “key personnel” in order to permit the flexibility to use multiple personnel from our large engineering staff that have the knowledge and training to satisfy JSA’s requirements.
      Designers will not be considered “key Personnel”.
  17. In anticipation of the responses to these questions, would JSA consider extending the proposal due date until January 31, 2008?
      Extend to 31Jan2008.
  18. Does Jeff Lab have a top level concept/arrangement drawing of the entire tagging magnet and vacuum layout, in the hall, that can illustrate the manner in which the various parts described in the spec and drawings tie together ?
      JSA will supply an interface drawing.
  19. Please confirm that the scope of work is limited only to the drawings and procedures described in the Statement of Work, and not an “entire functioning” design. An “entirely functioning” design would need to include all support services such as power supply, vacuum system (all components external to the chamber necessary to pull the vacuum), cooling system, water channel, wireways, controls, etc., etc. If the intent is to receive an “entire functional” design, please define and provide specifications for those systems and components.
      The scope of work is limited to the SOW, the specification and the drawings supplied. For clarification purposes, we expect that a power supply for the dipole is selected, minimum water flow and pressure requirements are defined and additional ports for pumping vacuum down are supplied on the vacuum chamber. No external pumping system or water cooling systems or wireways need be defined.

Accelerator Interface

The question arose from the accelerator planners, who will control the magnetic fields of the tagger dipoles and the quadrupole. Our answer is that the accelerator operator will control those parameters, as is presently the case in Hall B during real photon running.

However, the accelerator should not treat the tagger quadrupole field as a tunable parameter to optimize transmission of the beam into the dump. Rather, the tagger quadrupole field is an integral part of the tagging spectrometer optics. It may be useful for operators to play with the quadrupole field during initial delivery of the beam to the hall, but a certain predefined field gradient will need to be set up in the quadrupole before a tagged beam is ready for use by the experiment.