| Magnet Unit(s) | 7072,7092, ..8012..., 8032,8052 in both of PR04&PR06 |
|---|---|
| Typical BDES | -40.513 kG |
| Typical Current | 100 A |
| Typical PS Voltage | 120 V |
| Nominal Beta X | varies |
| Nominal Eta X | 0.0 m |
| Nominal Beta Y | varies |
| Nominal Eta Y | 0.0 m |
QDP is part of the magnet scheme which comprises the lattice for the HER tune adjusting straights 4 and 6. Each of these two straights has five QDP magnets; the QD at the arc midpoint, and first two QDs outboard of it in both directions.
The HER lattice in straights 4 and 6 is 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 HER has two such regions (straights 4 and 6) 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 11 magnets (5 QDs and 6 QFs) are powered in series (both trombones) with two power supplies (QFP for QFs, QDP for QDs). The four magnets at either end of the trombone (QFP9,QDP8,QFP7,QDP6) have independent power supplies (four power supplies per trombone such that say QFP9 powers two magnets; one on either end of the trombone symetrically about the straight midpoint).
The QFP9, QDP8, QFP7, and QDP6 magnets are powered locally for each straight, whereas the QDP and QFP magnets are powered in series for both straights.
Six power supplies (QFP,QDP,QFP9,QDP8,QFP7,QDP6) are sufficient to constrain the six parameters required for a sysmetric trombone. Another way to think of this would be to consider the (long stretch) of QFP and QDP magnets sufficient to achieve the tune (phase advance across trombone) adjustment for both X and Y planes. The remaining four QFP9-QDP6 are then used to cancel the effect of the beta and alpha X and Y which result from the QFP/QDP change.
The HER tune knobs are constructed from appropriate linear combinations of these 10 power supplies (QFP and QDP for both trombones, QFP9-QDP6 seperately but identically for each of the two trombones).