J. Welch Talk MMF 10/14/04 LCLS Magnetic Measurement Facility Requirements Functional Temperature Vibration Earth's Field

J. Welch Talk MMF 10/14/04 Functional Requirements During LCLS Construction Tune and measure undulator segments (40x) Fiducialize segments and quadrupoles (~80x) Assemble and align components (~40x) Vacuum chambers, BPMs, quadrupoles, undulator segments, diagnostics boxes, cradles Store some ready-to-go assemblies (~10x) During Operation Undulator segment validation program (1-3/month) New undulator magnets Other work for SLAC

J. Welch Talk MMF 10/14/04 Temperature Requirements Stability and Accuracy Set point and range

J. Welch Talk MMF 10/14/04 Temperture Stability and Accuracy Strength tolerance is |∆K/K| <= 1.5 x for 10 degrees phase error per undulator segment Temperature coefficient of remanence of NdFeB is 0.1%/C, which, because of partial compensation via Ti/Al assembly, leads to a measured undulator temperature coefficient of ∆K/K = -5.5 x /˚C,  |∆T| <= 0.27 ˚C Ambient air determines magnet temperature Undulator Hall is spec'd at |∆T| <= 0.2 ˚C Therefore MMF is spec'd at |∆T| <= 0.1 ˚C, Temperature control must be absolute and long term. Only selected areas within MMF require this level of control. CMM area needs ±1.0˚C.

J. Welch Talk MMF 10/14/04 Temperature Averaging The segments have a slow thermal response time Probes may be faster. Short term temperature fluctuations are allowed up to ±0.3 ˚C for less than 1 hour.

J. Welch Talk MMF 10/14/04 Temperature Set Point Temperture must match Undulator Hall year round 20.0 C chosen to match metrology standard Most people will find it too cold in the summer

J. Welch Talk MMF 10/14/04 Range of Set Points Measure the temperature coefficients of undulator segments in the future. HVAC should have a set point range from ˚C

J. Welch Talk MMF 10/14/04 Vibration Ambient vibration requirements set by probe stability ≤ 0.5  m rms. Transient requirements set at 3.0  m rms, not more often than 1 every 20 seconds. Repair of nearby "potholes" is called for.

J. Welch Talk MMF 10/14/04 Earth's Magnetic Field Earth's field must be corrected for at the level of 0.1 gauss or less The components in the horizontal plane are North 0.23 gauss, East 0.06 gauss. (Vertical 0.43 gauss is presumed same in MMF as UH). UH is 7.56 degrees off E-W line (WSW- ENE) Plan to align the measurement bench with Undulator hall, and avoid distorting the Earths field with large nearby steel components.