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Como habíamos comentado, la pista de baile era capaz de elevarse. Pero tambien podía bajarse dejando este peligroso hueco, que comunica con los sotanos. Es odvio, que no bajaba de esta manera habiendo publico ya que habían mas de tres metros de caída, suficientes para darse un buen testarazo. No entiendo como la dejaron así y no a ras de suelo, o por encima. Quizas para conseguir que alguien se mate?
Closed Orbit BPMs
Functionality :
The slow measurement of the X & Z e- beam position in the Storage Ring at 7 locations in each of the 32 Storage Ring cells, thus 224 BPMs around the 844m SR circumference. Each BPM block is rigidly connected to a quadrupole, there are 10 quadrupoles per cell.
The measurement is slow (1Hz rate) but of high reliability, precision and resolution and good reproducibility (for different beam conditions).
Purpose :
The system is used to stabilize the beam position on a slow time scale (i.e. in the DC frequency range) : at about 1 minute intervals the input from the C.O.BPMs is used to calculate deviations from a pre-measured Closed-Orbit (a defined reference orbit) and to effect corrections on the Closed-Orbit by the uses of correctors (96 both horizontal and vertical). The algorithm used is the singular value decomposition (SVD).
At a 1Hz rate the Closed-Orbit measurement is used for monitoring purposes with permanently updated displays informing the operation crew on the present beam stability.
Closed Orbit data is stored at the same 1Hz rate and in case of a beamloss event a 2 minutes history prior to the event is preserved.
Pick-ups, BPM block geometry, fixation, number of stations :
The four pick-up electrodes are 11mm in diameter and symmetrically positioned at 20mm (hor.) and 33mm (vert.) distance in a BPM block with 78 (hor.) and 33mm (vert.) aperture. Each BPM is rigidly fixed to its quadrupole.
The total of number of 224 stations is slightly reduced to 214 since 8 BPMs are dedicated for interlocks purposes, 1 is used for dispersion measurements and 1 is out-of-order due to a defective electrode.
The electrode is a self-consistent brazed piece with male-sma-connector output. Each of the 4 electrodes is welded at the outside to the BPM block. The Pick-Up, its connector and the cable are all bake-out compatible (150C).
Concept / Signal Treatment :
The four signals are processed by 3 dB attenuators and with 352MHz, 40Mhz BW filters before being time-multiplexed by a so-called RF-Multiplexer. This device is situated inside the tunnel and blinded against radiation damage by a 3mm thick lead case, the four 50ohms input cables from the P.U.s are 1m long.
The time-multiplexed signal is amplified and connected to a RF processor outside the tunnel (average cable length is 20m). The RF processor essentially performs down-conversion of the 352MHz signal to 10.7Mhz, amplification, filtering and level detection.
In fact each RF processor possesses two parallel signal chains : a narrow bandwidth and a large bandwidth (1MHz). Only the narrow band is used for the C.O.BPMs, the large bandwidth chain serves for injection purposes or for the so-called Thousand Turn BPMs (see corresponding page).
An ADC is clocked in phase with the RF-Multiplexer so that the four detected electrode signals are converted and stored in local memory. Six multiplex cycles of each 10ms are repeated every second.
The exact timing of the six cycles is determined so to strongly suppress any effect of small AC beam motions (e.g. a 7Hz horizontal motion) through aliasing.
Beam position results (the average of the six independent measurements) are calculated at this 1Hz rate from the four signal strengths in one central VME crate.
Performance :
- The absolute precision (with respect to the magnetic center of the Quadrupoles) is estimated at 50um rms and obtained by the so-called beam-based-alignment technique. With the BBA technique the current in a local quadrupole is slightly modified by the application of a local shunt, and the consequent perturbation to the Closed Orbit is assessed. In an iterative approach, in which local bumps are used to displace the beam at the BPM and Quadrupole, the BPM offset can be determined and corrected for.
- The resolution of the yielded BPM measurement (1Hz) is about 1um.
- The reproducibility at medium time scale (hours-days-weeks) is excellent thanks to the application of the RF-Multiplexer concept.
- The reproducibility at longer time scales (months, years) is mainly determined by external work and maintenance operations like vacuum bake-out, machine re-alignment (twice a year), exchange of vacuum chambers etc.
- The reproducibility with varying beam conditions (and in particular with beam intensity) is attributed mainly to the movement of the BPM blocks due to probably varying thermal stresses on the vacuum chamber and supports. This effect is assessed by Closed Orbit measurements at various beam intensities and, after deduction of the part that can be attributed to pure beam motion itself (harmonic number), a correction is applied to each individual BPM.
Pict0
Copyright © 2007 ESRF
Closed Orbit BPMs
Functionality :
The slow measurement of the X & Z e- beam position in the Storage Ring at 7 locations in each of the 32 Storage Ring cells, thus 224 BPMs around the 844m SR circumference. Each BPM block is rigidly connected to a quadrupole, there are 10 quadrupoles per cell.
The measurement is slow (1Hz rate) but of high reliability, precision and resolution and good reproducibility (for different beam conditions).
Purpose :
The system is used to stabilize the beam position on a slow time scale (i.e. in the DC frequency range) : at about 1 minute intervals the input from the C.O.BPMs is used to calculate deviations from a pre-measured Closed-Orbit (a defined reference orbit) and to effect corrections on the Closed-Orbit by the uses of correctors (96 both horizontal and vertical). The algorithm used is the singular value decomposition (SVD).
At a 1Hz rate the Closed-Orbit measurement is used for monitoring purposes with permanently updated displays informing the operation crew on the present beam stability.
Closed Orbit data is stored at the same 1Hz rate and in case of a beamloss event a 2 minutes history prior to the event is preserved.
Pick-ups, BPM block geometry, fixation, number of stations :
The four pick-up electrodes are 11mm in diameter and symmetrically positioned at 20mm (hor.) and 33mm (vert.) distance in a BPM block with 78 (hor.) and 33mm (vert.) aperture. Each BPM is rigidly fixed to its quadrupole.
The total of number of 224 stations is slightly reduced to 214 since 8 BPMs are dedicated for interlocks purposes, 1 is used for dispersion measurements and 1 is out-of-order due to a defective electrode.
The electrode is a self-consistent brazed piece with male-sma-connector output. Each of the 4 electrodes is welded at the outside to the BPM block. The Pick-Up, its connector and the cable are all bake-out compatible (150C).
Concept / Signal Treatment :
The four signals are processed by 3 dB attenuators and with 352MHz, 40Mhz BW filters before being time-multiplexed by a so-called RF-Multiplexer. This device is situated inside the tunnel and blinded against radiation damage by a 3mm thick lead case, the four 50ohms input cables from the P.U.s are 1m long.
The time-multiplexed signal is amplified and connected to a RF processor outside the tunnel (average cable length is 20m). The RF processor essentially performs down-conversion of the 352MHz signal to 10.7Mhz, amplification, filtering and level detection.
In fact each RF processor possesses two parallel signal chains : a narrow bandwidth and a large bandwidth (1MHz). Only the narrow band is used for the C.O.BPMs, the large bandwidth chain serves for injection purposes or for the so-called Thousand Turn BPMs (see corresponding page).
An ADC is clocked in phase with the RF-Multiplexer so that the four detected electrode signals are converted and stored in local memory. Six multiplex cycles of each 10ms are repeated every second.
The exact timing of the six cycles is determined so to strongly suppress any effect of small AC beam motions (e.g. a 7Hz horizontal motion) through aliasing.
Beam position results (the average of the six independent measurements) are calculated at this 1Hz rate from the four signal strengths in one central VME crate.
Performance :
- The absolute precision (with respect to the magnetic center of the Quadrupoles) is estimated at 50um rms and obtained by the so-called beam-based-alignment technique. With the BBA technique the current in a local quadrupole is slightly modified by the application of a local shunt, and the consequent perturbation to the Closed Orbit is assessed. In an iterative approach, in which local bumps are used to displace the beam at the BPM and Quadrupole, the BPM offset can be determined and corrected for.
- The resolution of the yielded BPM measurement (1Hz) is about 1um.
- The reproducibility at medium time scale (hours-days-weeks) is excellent thanks to the application of the RF-Multiplexer concept.
- The reproducibility at longer time scales (months, years) is mainly determined by external work and maintenance operations like vacuum bake-out, machine re-alignment (twice a year), exchange of vacuum chambers etc.
- The reproducibility with varying beam conditions (and in particular with beam intensity) is attributed mainly to the movement of the BPM blocks due to probably varying thermal stresses on the vacuum chamber and supports. This effect is assessed by Closed Orbit measurements at various beam intensities and, after deduction of the part that can be attributed to pure beam motion itself (harmonic number), a correction is applied to each individual BPM.
Pict0
Copyright © 2007 ESRF
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For a private collector. NFS.
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