CERN
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BEAM INSTRUMENTATION GROUP
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Date : 201x-xx-xx
[Functional Specifications]
ON MEASUREMENTS OF THE BEAM CURRENT
IN THE PS BOOSTER
ABSTRACT:
This document presents an analysis of the anticipated use of the beam current
knowledge for machine operation and studies in the PS Booster rings after the LHC
Injectors Upgrade program. The targeted parameter space is identified and the required
accuracy to cover these anticipated use estimated. These requirements are converted
into functional specifications for beam instrumentation. The whole spectrum of possible
beams is considered as well as any relevant design constraints.
DOCUMENT PREPARED BY:
DOCUMENT CHECKED BY:
DOCUMENT APPROVED BY:
JJ Gras
BE-BI HW Experts
LIU-PSB PL
LIU-PSB-BCT Resp
BE-BI SW Experts
BE-BI BCT SL
PSB-OP Resp
…
BE-BI SW SL
DOCUMENT RELEASED BY:
R. Jones
DOCUMENT SENT FOR INFORMATION TO:
[List of persons to whom the document is sent]
This document is uncontrolled when printed. Check the EDMS to verify that this is the correct version before use.
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HISTORY OF CHANGES
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2011-04-01
All
DESCRIPTIONS OF THE CHANGES
Initial submission
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TABLE OF CONTENTS
1.
Introduction .......................................................................................................... 4
2.
Beam Current Related Parameter Space ................................................................... 4
2.1
Main Observable and Related Parameters ............................................................. 4
2.2
Related Parameter Space .................................................................................... 4
2.3
Relevant PPM context information ........................................................................ 5
3.
Anticipated Uses of The Beam Current Monitors ......................................................... 5
3.1
Measurement of the injection efficiency into the Booster ......................................... 5
3.2
Observation of the current decay over the first turns.............................................. 6
3.3
Measurement of the circulating beam/gated currents ............................................. 6
3.4
Measurement of the extraction efficiency towards the PS ........................................ 6
3.5
Machine Statistics .............................................................................................. 6
3.6
Machine Protection............................................................................................. 6
4.
Functional Requirements ........................................................................................ 6
4.1
Acquisition parameters : Sampling, Gating ........................................................... 6
4.2
Precisions : accuracy, resolution, dynamic range ................................................... 6
4.3
Real Time Considerations : Synchronisation with GMT, beam synchronous timing, PPM
handling ........................................................................................................... 6
4.4
Data to be made available .................................................................................. 7
4.5
Data to be logged .............................................................................................. 7
5.
Design Constraints................................................................................................. 7
6.
Reliability, Availability and Maintenance.................................................................... 7
7.
References............................................................................................................ 8
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1. Introduction
This document presents an analysis of the anticipated use of the beam current
knowledge for machine operation and studies in the PS Booster rings after the LHC
Injectors Upgrade program. The targeted parameter space is identified and the
required accuracy to cover these anticipated use estimated. These requirements are
converted into functional specifications for beam instrumentation. The whole spectrum
of possible beams is considered as well as any relevant design constraints.
In order to avoid misunderstandings, these specifications will be based on basic
instrumental terminology defined in [1].
2. Beam Current Related Parameter Space
2.1 Main Observable and Related Parameters
This chapter describes the main beam observable covered by this document and the
beam parameters that will be derived from it and considered in here.
The primary observable covered by this document is the number of charges measured
by the instruments during the passage of a fraction or of the entire beam.
The beam parameters related to the measured beam charge are:

The gated (bunch, batch) and beam (all circulating charges) currents

The gated and beam loss rates between two consecutive period of time or
locations

The current of non-nominal bunches (satellites and ghosts) or debunched
beams
2.2 Related Parameter Space
The ranges and attributes of the expected PSB beam currents is shown in Table 1.
Table 1 — [Caption of the table]
Particle
Bunch
Number of
Total Beam
charge
bunches
Charge
q
Protons
for LHC
2 109 
? 1011
Bunch spacing
length
ns
1?
??
RMS Bunch
? -> ?
4σ, ns
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? 109 
Pb for
LHC
1??
??
??
?
?
??
?
?
?
?
?
? -> ?
? 109
Protons
for non
LHC
clients
?
?
2.3 Relevant PPM context information
Basic description of PSB USER sequence.
Do we have to handle settings/acquisitions depending on something else than the
USER like Destination, Particle Types (this is to be avoided as much as possible) ?
3. Anticipated Uses of The Beam Current Monitors
This chapter list the anticipated uses of the instruments specified in this document. A
subchapter per use cases will describe the aim of the measurement and state the
precision requested (accuracy and/or resolution and/or repeatability… see [1]).The
main source for these precision estimations should also be given.
3.1 Measurement of the injection efficiency into the Booster
Here is a possible explaination
The injection efficiency is defined to be the ratio of the beam current measured in the
ring to the beam current measured at the end of the transfer line.
The current monitors must have the following characteristics:

Absolute accuracy and cross-calibration between transfer and ring monitors of
±?% for nominal bunches, which implies an absolute accuracy better than ±?%
per monitor for high intensity beam (threshold to be defined), i.e. ±XeY protons.

A repeatability (cycle to cycle) of ±?%.
This demand on accuracy can be compared to the acceptable or target loss rate in the
injection region [xxx]. The requested absolute accuracy provides a safety factor of 2
compared to this level when injecting blabla (for instance)….
For the injection of low intensity beam the demand on accuracy can be relaxed to
±xx%.
These measurements shall integrate the whole injected beam and be automatically
measured and published at each injection for every played cycle.
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3.2 Observation of the current decay over the first turns
3.3 Measurement of the circulating beam/gated currents
3.4 Monitoring of beam intensity and loss rates at predefined markers along
the cycle.
3.5 Measurement of the extraction efficiency towards the PS
3.6 Machine Statistics
3.7 Machine Protection
4. Functional Requirements
This chapter makes a synthesis of the given use cases. It extracts the most
demanding requirements and compiles the corresponding functional requirements per
topics.
4.1 Acquisition parameters : Sampling, Gating
4.2 Precisions : accuracy, resolution, repeatability, dynamic range
4.3 Real Time Considerations : Synchronization with GMT, beam synchronous
timing, PPM handling
BI should be able to derive from this paragraph the front end SW (FESA) real time
behavior of these devices.
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4.4 Data to be made available
BI should be able to derive from this paragraph the front end SW (FESA) interface of
these devices.
For properties including choices (like acquisition within a specific window for instance),
the need to allow or not multi-user, multi-usage should be clarified.
4.5 Data to be logged
5. Design Constraints
This chapter should list the identified design constraints for this instrument.
5.1 Radiation Levels
An estimation of the radiation levels expected around the tunnel after the upgrade
should be provided here for us to know if we can install electronics there. Ideally this
would be a map representing all the ring but we could start with extreme expected
level in main zones like Arcs, DS, SS and inj/extr areas. Radiation levels, target
locations, use of existing devices or instrument type with proven results...
5.2 Layout
This chapter could state that for some reasons, we will have to limit ourselves to some
specific zones or even to reuse existing slots or monitors.
In addition, details on optics could be necessary in some cases.
5.3 Design Constraints
I add this one for us 
It is important to think about and provide as early as possible the ways to check that
the installed instrument actually fulfill the specifications. Each instrument should come
with:

An as exhaustive as possible list a potential sources of errors

Methods to evaluate them (monitoring points, laboratory test benches, dedicated
measurement campaigns…)

Targeted actions to limit them
6. Reliability, Availability and Maintenance
This chapter should give some statement (and justification) on the expected Reliability
of the systems (see [1]) like
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The circulating beam and bunch current monitors are ?critical?important? for machine
operation. At least ??? must be fully available during operation with a reliability
reaching a Safety Integrity Level of 2.
The single-pass bunch current monitors are important as well, though not critical. ...
7. References
[1] Concepts and Glossary for the Specification of the Beam Instrumentation
(https://edms.cern.ch/document/1141178 )