REAL TIME MOMENTUM SPREAD
MEASUREMENT OF THE CERNANTIPROTON DECELERATOR BEAM
P. Freyermuth*, B. Dupuy, CERN, Geneva, Switzerland
D. Gamba, CERN, Geneva, Switzerland

Currenttransformers

2110.5
MomentumThe result is a transposition of thesignal to a fixed centre frequency of50 kHz, enabling fixed parameters fordifferent cooling plateau energies.

Summing unit

The ADC FMC card(n * f0) - 50kHz

FMC ADC card
OASIS FESA class
Real-time
Control and acquisition

The signal acquisition is performed by a 4 channel
100 Msps 14-bit ADC card. Typical settings are asampling rate of 3 Msps during a 100 ms segment, fora total of 3E5 samples per segment. The acquisition
segment is repeated and published continuously at 5Hz. The voltage range is set to the maximum
sensitivity at +/- 50 mV.

ServerFFT library

Real-time
OASIS subscription

A raw data segment

8051

50

49
0123Time (Day)

dB-20
To
clients-30

48

49
50
51
Frequency (kHz)52[1] C. Gonzalez and F. Pedersen, “An ultra-low noise ac beam transformer for deceleration and diagnostics of low intensity beams.”, in1999 Particle Accelerator Conference, New York, USA, 29 March - 2 April 1999. doi: 10.1109/PAC.1999.795736[2] D. Boussard, “Schottky noise and beam transfer function diagnostics 1995 ed.”, in CAS - CERN Accelerator School: 5th Advanced
Accelerator Physics Course, pp.749-782. doi: 10.5170/CERN-1995-006.749* pierre.freyermuth@cern.ch4

5Snapshots of Schottky spectrum at key moments along
the AD deceleration cycle are logged, it allows machinestability analysis over several days and observation of any
drifts of the cooling systems.

-40
Overview of the acquisition andprocessing system

100A java application has been developed for the operators,
available on control rooms computers. Schottky spectra aredisplayed in a three-dimensions chart. The time axis is kept
horizontal to be synchronised with other two dimensions
time charts. The power spectrum value is colour coded,
and the vertical axis represents the frequency.

-10Spectrum

Data publication

4060
Cycle time (S)The computation of the Schottky spectrum is performed and the data from frequencies around 5kHz
are published to clients.

FFTServer

20

One can enhance thedetails of the envelop of thelongitudinal cooling processes
performance by averaging
several cycles during stable
operation.

Data publication

Schottky spectrum
FESA class

00Frequency (KHz)

32dB

Front-end Computer

Rev. Freq.

0

mixing andfiltering unit

Fromsumming
unit

From
Downmixing

1.5

To accommodate the different revolution
frequencies of the AD cooling plateaus, thesignal from the LPU is mixed with a signal
generated from a harmonic of the revolution
frequency minus 50 kHz.

The AD Longitudinal pick-up

Amplifier units

3Revolution frequency(MHz)The AD longitudinal pick-up (LPU) consistsof two specially designed ultra-low noise
ferrite-loaded beam current transformers andamplifiers [1].
The longitudinal Schottky spectrum of a debunched beam consists of bands offrequencies (Schottky bands), located aroundharmonics of the average revolution frequency.
[2]

September 10-14, 2023
Saskatoon, Canada
Lightsource.ca/IBIC2023

The AD decelerating cycle
Momentum (GeV/C)

Constant optimisation and diagnostics of the cooling processes in the CERN
antiproton decelerator (AD) relies on a de-bunched beam momentum spread real timemeasurement.
The AD longitudinal Schottky measurement for operation has been renovated anddeployed with standard CERN hardware and software to maximize reliability and easemaintenance. It is used for day-to-day operation through several applications.

TPU045

Displayed on large screens in control
rooms and published worldwide via aCERN webpage, the status screen of theAD/ELENA now integrates the AD real time
animated Schottky spectrum.