Comparison of Different Bunch Charge
Monitors used at the ARES Accelerator atDESY

Timmy Lensch, Dirk Lipka, Reinhard Neumann, Matthias Werner
Saskatoon, 12th September 2023

Outline
00 Motivation
01 ARES Overview
02 Faraday Cup• Simulations, Mechanics, Electronics• Calibration

03 Beam Charge Transformator (Toroid)• Mechanics and Electronics• Calibration

04 Dark Current Monitor (DaMon)• Mechanics and Electronics• Calibration

05 Turbo-ICT and ICT (Bergoz)• Setup and read out

06 Measurements• Linearity compared with Faraday Cup• Resolution of DaMon, Toroid and T-ICT07 Summary

DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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00 Motivation

Motivation•

The ARES eFLASH (medical) experiment needs an absolute, non-destructive charge measurement•

ARES normally operates at lower charges compared to other DESY machines (30 fC - 200 pC)•

ARES is an R&D machine  install different types of charge monitors (increase dynamic range&resolution)

Beam Charge Monitors at DESY•

Use in-house developed Charge Monitors (beginning in the 1980s)• i.e. E-XFEL, FLASH = 60 monitors (Toroid type)• Transport Lines in other machines•

No (non-destructive) absolute measurement with such a dynamic range needed so far•

Important: Transport efficiency

This talk only presents dedicated charge monitors.
At the ARES accelerator there are also Cavity BPMs installed.
This Conference:
IBIC2022:

Poster MOP019 by Bastian Lorbeer
Poster WEB14

DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

Page 4

01 ARES Overview

Cathode & pump lasers

The ARES Linac

A dedicated accelerator R&D machine
ARES goal: Generate and characterize ultrashort e- bunches (fs to sub-fs) with high stability forapplications related to accelerator R&D (advanced & compact longitudinal diagnostics andaccelerating structures development, test of new accelerator components, machine learning, etc.),
medical applications studies and beam time for external R&D users.
Parameter

StatusChargeGun

0.01 - 250 pC

Momentum

Gun Diagnostics
FC, DaMon

20 - 160 MeV/c

Bunch Length≈ 20 fs (res. limited)

Rep Rate (Single Bunch)Contact: florian.burkart@desy.dehttps://ares.desy.de/

Courtesy: Willi Kuropka
Experimental Areas 2&3

Traveling Wave Structures (TWS)

10 Hz

DaMon, Toroid

Experimental Area 1

Bunch Compressor(not operational yet)

ToroidX-Band PolariX TDS (2 Cavities)(not operational yet)

T-ICT (in vacuum)
ICT (in air)
DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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02 Faraday Cup (FC)Faraday Cup

Simulation of new design for ARES•Improvement of efficiency•Optimized design with Cu cup + Al Inlay, 15 mm diameter, 24 mm depth simulated•Found 0.6% of primary and secondary electrons escaping from the Faraday Cup at 5MeV

•Also different beam configurations and angles show very good results of <1% loss

Green=Gammas, Red = Electrons
Courtesy: Maike Pelzer

Courtesy: Sergey Strokov, Gero Kube

DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

Page 8Faraday Cup

Simulations of former designs used at DESYe-If you have other geometries…
•existing Faraday Cup variants at DESY•

Simulated for 5 MeV beam (ARES)•Variants of materials (Copper - Aluminum combinations)•Different geometries and angles of electron beam•

Between 4 - 22% of primary and secondary electrons escape fromthe Faraday Cup•

 not sufficient for ARES

Courtesy: Sergey Strokov, Gero Kube

e-electrons
gammasDESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

Page 9Faraday Cup
Final design•

Faraday Cup mounted on a Mover•

Without cooling due to low repetition rate (10 Hz)•Screen at same position to check beam size + position

Tunnel installation with Faraday Cup horizontal,
Screen verticale-Courtesy: Maike Pelzer (FC), Christian Wiebers (Mover), Juergen Kruse (Support)
DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

Page 10Faraday Cup

Electronics and Calibration•FC signal connected to front end with 15 MHz low passfilter and pre amp (tunnel)•Read out with MTCA system (outside tunnel)• Struck ADC SIS8300-L2D, 16 bit, 125 MS/s
• Pulse-form-fit with 3-point sampling
TunnelCalibration•

Send electrical pulse to the FE electronic•

Corresponds to 1nC pulse•

Scaling the read oute-Calibration
PulserFE BoxDESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

MTCAADCPage 11

03 Beam Charge Transformator(Toroid)ToroidOptimization of existing Beam Charge Transfomators•

E-XFEL and FLASH design (4.5 MHz bunch frequency)•

Ceramic gap with one or dual core, easy half-shell installation(i.e. service w/o opening vacuum)•

Four separate coils, one winding each, concatenated outside(red)•Front end box with 15 MHz low pass filter and pre amp (tunnel)•

Read out with MTCA system (outside tunnel)• Struck ADC SIS8300-L2D, 16 bit, 125 MS/s
• Pulse-form-fit with 3-point sampling (like at FC)

Calibration•

Send electrical pulse to calibration winding (blue)•Corresponds to 1nC pulse•

Scaling the read out…

Courtesy: Maike Pelzer

Tunnel…

…
e-CalibrationPulser

FE BoxDESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

MTCA
ADCPage 13

04 Dark Current Monitor(DaMon)

Dark Current Monitor (DaMon)

Invented to measure dark current of accelerators with 1.3 GHz acceleration frequency•Consists of stainless steel resonator TM010 mode at1.3 GHz, loaded quality factor about 200, results inbandwidth of about 6 MHz and decay time 50 ns•

RF Front End Electronic (RFFE) with two channels:• dark current (DC) with local oscillator, down conversion andlogarithmic detector• Charge (Q) with logarithmic detector•Send to MTCA system with 16 bit ADC (Struck 8300-L2D)

Refs: Lipka et al. DIPAC 2011 WEOC03 and IBIC 2013 WEPF25
DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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Dark Current Monitor (DaMon)Calibration•

For 3 GHz accelerator (ARES) both channels (DC and Q)
are used for charge measurement: increase dynamic range•

Arbitrary Waveform generator (AWG) in laboratory
simulates output of DaMon•

AWG as input for the RFFE at largest possible amplitude
range

•

Output of RFFE connected to ADC and monitors amplitude•

Results in an electronics response function look-up table•

Together with measured properties of each individual
resonator (frequency, quality factors) and cable attenuation
results in look-up table for each channel
Poster TUP037 by Dirk Lipka this afternoon

Calibration in rackroom

Test in laboratory

DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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Dark Current Monitor (DaMon)
Calibration•

For 3 GHz accelerator (ARES) both channels (DC and Q)
are used for charge measurement: increase dynamic range•

Arbitrary Waveform generator (AWG) in laboratory
simulates output of DaMon•AWG as input for the RFFE at largest possible amplituderange•

Output of RFFE connected to ADC and monitors amplitude•

Results in an electronics response function look-up table•

Together with measured properties of each individualresonator (frequency, quality factors) and cable attenuation
results in look-up table for each channel

Calibration in rackroom

Poster TUP037 by Dirk Lipka this afternoon
DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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05 Turbo-ICT (Bergoz)

Bergoz Turbo-ICT

Integrating Current Transformer + Front end Filter (Bergoz)

10 Hz timing trigger

Turbo-ICT in vacuum•

BERGOZ Turbo-ICT and BCM-RF-E (outside tunnel, ~30m cable)• Use in Sample & Hold Mode
• Range: 50 fC ... 300 pC• Noise: 10 fC rms or 1% of charge (whichever is higher)•Connected to a KEITHLEY High Resolution DVM (DMM7510)• Resolution 1 µV (at range 10 V)

Trigger when conversion
ready• Ethernet for control system read out•

Triggering• 10 Hz trigger from timing system•

Apply Look-up-Table in Software with data fromBergoz’ calibration

Control system(DOOCS)

https://www.bergoz.com/products/turbo-ict/https://www.tek.com/de/products/keithley/digital-multimeter/dmm7510#
DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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05 ICT (Bergoz)

Bergoz ICT in air

Improvised installation for testing purposes
In-air ICT•

Placed after a window outside the end of beam pipe(~30 cm after T-ICT)•

Read-out, integration and scaling with 12 bit scope•Can easily be moved to other DESY machines

12 bit scope
10 Hz timing trigger

ICT signal

https://www.bergoz.com/products/ict/
DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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06 Measurements

What has been measured?
•ARES at 10 Hz rep rate•

Charge Sweep from 0.1 – 153 pC•~100% Beam Transport (w/o Bunch Compressor and X-Band TDS)

•500 values per charge from each monitor saved synchronously•

Output will be plots of …
• Linearity of each monitor compared to Faraday Cup (w/o uncompensated losses [0.6% simulation])• Resolution of each monitor

DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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DaMon DC vs. Faraday Cup
Range 0.1 – 13 pC

DaMon DC0

DaMon DC1

Linear fit slope

1.04

1.06

Linear fit offset-0.002 pC-0.006 pC•Calibrated in the lab, not beam based•

Measure ~<20 pC only•

Error is standard deviation caused by beam
charge jitter (relative plot)

Error is standard deviation caused by beam charge jitter
DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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DaMon Q vs. Faraday Cup
Range 1 – 153 pC

DaMon Q0

DaMon Q1

Linear fit slope

0.96

1.04

Linear fit offset

0.26 pC

0.31 pC•

Calibrated in the lab, not beam based

Error is standard deviation caused by beam charge jitter
DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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Toroid vs. Faraday Cup
Range 1 – 153 pC

Toroid0Toroid1

Linear fit slope

1.18

1.15

Linear fit offset-0.02 pC

-0.02 pC

•Calibrated with 1nC pulse•

Calibration scheme seems to be not matched as
expected under investigation•… but linear

Error is standard deviation caused by beam charge jitter
DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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Bergoz Turbo ICT vs. Faraday Cup
Range 1 – 153 pC

T-ICTLinear fit slope

1.012

Linear fit offset

0.11 pC•

Calibrated at Bergoz•Implemented look up table

Error is standard deviation caused by beam charge jitter
DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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Bergoz ICT in Air vs. Faraday Cup
Range 30 – 153 pC

ICT•

Calibrated at Bergoz•Read out with 12 bit scope

Linear fit slope

1.03•Values <30 pC not measurable in the current scheme (cable …)

Linear fit offset

5.9 pC•not fully trustworthy due to improvised read out  Ongoing work

Error is standard deviation caused by beam charge jitter
DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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Resolution Measurement

Use standard deviation (rms) to calculate resolution•

Take all non-destructive charge monitors synchronously per charge step as reference value•Compare monitor under test to the reference value•

Independent from machine optics•We included Cavity BPM charge channel data to enhance the reference value•Details of this procedure:• „Resolution Studies at Beam Position Monitors at the FLASH Facility at DESY“, N.Baboi, BIW2006

DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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Resolution of DaMon DC Channel
Charge range from 0.1 – 13 pC

100 fC – 13 pC•DaMon DC Channels
limited to <20 pC•

Very good at <10 pC

DaMonDC0DaMonDC1

Resolution [fC]

4 – 111

4 – 90Resolution [%]3.4 – 0.83

3.36 – 0.59

DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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Resolution of DaMon Q Channel
Charge range from 1 – 153 pC

1 pC – 153 pC•

DaMonQ0DaMonQ1Resolution [fC]

34 – 366

37 – 427

Resolution [%]3.38 – 0.24

3.74 – 0.28

For high charges resolution
converges to <0.3%

DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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Resolution of Toroid
Charge range from 1 – 153 pC•1 pC – 153 pC

Toroid0(dual core)

Toroid1(single core)

Resolution [fC]

108 – 119151 – 154

Resolution [%]10.8 – 0.08

15.08 – 0.1

For high charges resolution
converges to 0.1%

DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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Resolution of T-ICT
Charge range from 1 – 153 pC

1 pC – 153 pC••

For high charges resolution
converges to ~1%

T-ICT

Resolution [fC]

31 – 1621

Resolution [%]3.08 – 1.06

Resolution value larger
due to extended cable (~30m)(expected 10 fC @5m cable)

DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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Compare Resolution
If we want to do a ranking …
•

DaMonDC: ≤ 6 pC

•DaMonQ: 6 – 60 pC•Toroids: >60 pC Toroids best resolution•T-ICT:w/o DaMonDC• also good for <1 pC• used for absolute values

with DaMonDC

Legend colors differs!

DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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07 Summary

Summary

Linearities and Resolutions of all monitors @ARES•DaMon DC

DaMon Q

ToroidT-ICT

ICT

Measurement
range [pC]

0.1 to 13

1 to 153

1 to 153

1 to 153

38 to 153

Linear fit Slope

1.04
1.06

0.96
1.04

1.18
1.15

1.01

1.03

Linear fit Offset[pC]-0.002-0.006

0.26
0.31

-0.02
-0.02

0.11

5.9

Resolution rel.
(min/max charge)

3.4% to 0.8%
3.3% to 0.6%3.4% to 0.2%
3.7% to 0.3%

10.8% to 0.1% (Dual core)
15.1% to 0.1% (Single core)

3.1% to 1.1%

notaccessible

Use forResolution≤ 6 pC

Resolution
6 – 60 pC

Resolution>60 pC

Absolutemeasurement

takeaway-ref

ICT measurement not to be taken as face value yet

DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

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Summary•

Four different types of charge monitors, 1 destructive, 4 non-destructive installed in ARES•New simulated Faraday Cup design, catches >99% of charged particles•

DaMons show very good results compared to Faraday Cup•

Toroids show 15-18% linear slope deviation, but linear with good resolution at higher charges•T-ICT also shows very good agreement with Faraday Cup  absolute measurement•

Except ICT all monitors are used for machine operation•

Outlook: improve ICT read out and Toroid calibration

DESY. | Comparison of different Bunch Charge Monitors used at ARES Accelerator at DESY | T. Lensch, IBIC2023, Saskatoon, 12th September 2023

Page 38Thank you
Many people contributed to development, installation, commissioning andmeasurements
From the ARES team
Florian Burkhart, Willi Kuropka, Hannes Dinter, Frank Mayet, Max Kellermeier, Sonja Jaster-Merz
From Diagnostics Group (MDI)
Maike Pelzer, Jürgen Kruse, Norbert Wentowski, Zlatan Pisarov, Klaus Knaack, Artem Novokshonov,
Jörg Neugebauer, Sergey Strokov, Christian Wiebers, Bastian Lorbeer, Hans-Thomas Duhme, Igor
Krouptchenkov, Jorgen Lund-Nielsen†
References
F. Burkart, R.W. Aßmann, H. Dinter, S. Jaster-Merz, W.Kuropka, F. Mayet, and et al., “The ARES Linac at DESY”, in Proc. LINAC’22, Liverpool, UK, Aug.-Sep. 2022, pp. 691-694. doi:10.18429/JACoWLINAC2022-THPOJO01
https://www.picmg.org/openstandards/microtca
https://www.struck.de/sis8300-l2.html
M. Werner et al., "A Toroid Based Bunch Charge Monitor System with Machine Protection Features for FLASH and XFEL", in Proc. IBIC2014, Monterey, CA, USA, 2014, pp. 521–524.
M. Werner et al., "Sensitivity Optimization of the Standard Beam Current Monitors for XFEL and FLASH II", in Proc. DIPAC2011, Hamburg, Germany, 2011, pp. 197–199.
D. Lipka et al., "Charge Measurement with Resonators at ARES", in Proc. IBIC2023, Saskatoon, CA, September 2023, paper TUP037, these proceeding this conference
K. B. Unser, "Measuring bunch intensity, beam loss and bunch lifetime in LEP", Report CERN-SL-90-27-BI", 1990, https://cds.cern.ch/record/209858
N. Baboi et al., “Resolution Studies at Beam Position Monitors at the FLASH Facility at DESY”, in Proc. BIW’06, Batavia, IL, USA, May 2006, AIP Conf. Proc., vol. 868, pp. 227–237. doi:10.1063/1.2401409
B. Lorbeer et al., "Cavity BPM Electronics for SINBAD at DESY", in Proc. 11th Int. Beam Instrum. Conf. (IBIC’22), Kraków, Poland, Sep. 2022, pp. 413–415. doi:10.18429/JACoW-IBIC2022-WEP14