| Magnet Unit(s) | 2082,3042 |
|---|---|
| Typical BDES | 21.178 kG |
| Typical Current | 80 A |
| Typical PS Voltage | 60 V |
| Nominal Beta X | 23 m |
| Nominal Eta X | 0.0 m |
| Nominal Beta Y | 2.5 m |
| Nominal Eta Y | 0.0 m |
QFP3R04 is part of the magnet scheme which comprises the lattice for the LER tune adjusting straight 4.
The LER lattice in straights 4 and 12 are dedicated to tune (number of betatron oscillations per go-around) adjustment. The idea is that these parts of the lattice can be adjusted to achieve an overall tune change without changing the phase advance (or beta functions, dispersion, etc.) outside these regions. Such a region has been coined to be a "phase trombone". The LER has two such regions (straights 4 and 12) and they are setup identical to one another.
In order to achieve this trombone scheme the beta and alpha (z derivative of beta) must be constrained at the beginning and end of the trombone. Constraining beta and alpha, X and Y, before and after specifies eight different constraints. Add to that the desire to change the phase advance in X and Y yields a total of ten constraints (or parameters) to specify. It turns out however that if the trombone is constructed symetrically, then the before/after beta/alpha constraints cancel, leaving only 6 constraints or parameters.
The layout of these "phase trombone" straights are symetric about the straight midpoint.The layout of the trombone is as follows: The central magnet is a QD. This QD and the two QDs on either side are powered in series with one power supply ("QDPR04"). The two QFs on either side of the central QD magnet are powered by one power supply ("QFPR04"). Progressing towards the arcs in both directions the magnet sequence for the remaining seven trombone members on each side progresses as QFP3, QDP4, QFP5...up to QFP9. Each of these seven outward trombone elements has it's own power supply for each element (i.e. "QDP4R04" powers the two QDP4 magnets in straight 4).
While only 6 parameters are necessary to implement a symetric trombone, the LER has 9 independent power supplies (degrees of freedom) available for the purpose.
(Presently) the LER tune knobs are constructed from appropriate linear combinations of the seven QFP3 through QFP9 magnets using both trombones identically.