8th MT Student Retreat

27 Sept 2022, 18:00 → 28 Sept 2022, 22:00 Europe/Berlin

CFEL SR III (DESY)

**** News *** Change of Venue of the MT annual meeting (and student retreat!) to DESY, Hamburg *** News ****

The eighth Student Retreat within the Helmholtz program "Matter and Technologies" is a meeting of PhD students to get to know each other and to exchange ideas and solutions. It will take place following the 8th Annual MT Meeting .

The Student Retreat takes place at the CFEL, building 99, in SR III. For online participation use:
https://desy.zoom.us/j/63741776858
Meeting-ID: 637 4177 6858
Passcode: MTSR[at]DESY

Tuesday, 27 September

Dinner & Get-Together

Wednesday, 28 September

Welcome & Introduction

Conveners: Christina Schwemmbauer (ALPS (ALPS _ Any Light Particle Search)), Max Vitz (Forschungszentrum Jülich, RWTH Aachen)

1 Welcome

Speaker: Max Vitz (Forschungszentrum Jülich, RWTH Aachen)

2 Introduction to MT

Speaker: Andreas Kopmann (Karlsruhe Institute of Technology (KIT))

MT-primer-v2-compr.pdf

Morning session

Convener: Christina Schwemmbauer (ALPS (ALPS _ Any Light Particle Search))

3 Radiative particle-in-cell simulations of the beam hosing instability

We present the results and analyses of radiation spectra expected to be
produced by highly relativistic particle beams propagating through a
plasma medium and experiencing the hosing instability.
Coherent and incoherent contributions to the spectra are determined
in-situ for all simulated particles (>10^9) of the particle cloud and
ambient plasma for a lage assembly of detectors.
With the help of our particle-in-cell code we are able to distinguish
radiation emitted by plasma particles from that of the bunch.
In the simulation campaign, conducted at the JUWELS Booster cluster at
JSC, we consider linear and non-linear regimes of the instability for
highly relativistic electron beams impacting a homogeneous electron plasma.
We show an updated analysis of the data relating observed
characteristics of the spectra to the features of the bunch and ambient
plasma, thereby identifying first features indicative of the hosing
instability in PWFA.
A goal of these studies is to open up new experimental avenues for
better understanding the beam instability evolution by identifying
quantitative radiation signatures of the instability that can be
measured in experiments.

Speaker: Anton Lebedev (Helmholtz Zentrum Dresden-Rossendorf)

Presentation_v5 (minimiert).odp

RadiationOfHosing_Lebedev_StaticVersion.pdf

4 Low Gain Avalanche Diodes for Beam Monitoring and T0 Determination in HADES

Low Gain Avalanche Diodes (LGADs) are fast sensors allowing the detection of particles with high time and spatial resolution, thus enabling the so-called 4D particle tracking. Due to their high radiation hardness and low material budget, LGADs are excellent sensors for in-beam detectors used for example for beam monitoring and reaction time (T0) determination in high-rate High Energy Physics (HEP) experiments.
An in-beam detector based on LGADs was used in a high-rate pp production beam time in February
2022 at the High Acceptance Di-Electron Spectrometer (HADES). The LGAD sensors consisted of 96 half-strips with a pitch of 387 μm. They were successfully used for beam macro- and micro-spill structure and position monitoring during the beam time. In addition, the precise timing information will be used to assist in the Time-Of-Flight (TOF) based particle identification in HADES.

In this contribution, the LGAD sensors constituting the in-beam detector will be introduced and the calibration process as well as the sensor performance will be presented. In addition, an outlook on further ongoing activities will be given.

Speaker: Wilhelm Krüger (Technical University Darmstadt)

Wilhelm_Krueger_MTStudentRetreat.pdf

5 Particle identification with fast timing detectors at future Higgs factories

Future $e^+e^-$ Higgs factory collider projects are designed for preci-
sion measurements of the Higgs boson and of electroweak observables,
thereby utilizing every event to their full potential. The identification
of the pions, kaons and protons plays a key role for precision measure-
ments and event reconstruction, especially for the flavour tagging. To
improve the identification of charged hadrons at low momentum we
can use the time-of-flight method. It relies on current silicon sensor
technologies with extremely good time resolution of 10 - 30 ps. This
allows to measure the time-of-flight of particles and reconstruct their
mass providing additional tool for identification of $\pi^{\pm}$, $K^{\pm}$ and $p$.
We study possible realistic implementation scenarios and potential
physics applications of the fast timing silicon sensors into the future
Higgs factory detectors using as an example the International Large
Detector (ILD) at the International Linear Collider (ILC).

Speaker: Bohdan Dudar (FTX (FTX Fachgruppe SLB))

MT22.pdf

10:45 Coffee break

Morning session

Convener: Ulrich Einhaus (FTX (Fachgruppe SLB))

6 Exploring the dynamics of SSMB in a Proof-of-Principle experiment at the Metrology Light Source

The method of Steady-State Microbunching (SSMB) as proposed by Alex Chao and Daniel Ratner in 2010 is envisioned to generate intense coherent synchrotron radiation at a storage ring. The scheme would allow synchrotron light with brilliance similar to an FEL while enabling high repetition rates typical for a storage ring.

A proof-of-principle (PoP) experiment is conducted at the MLS storage ring in Berlin and has successfully demonstrated the viability of the general mechanism behind SSMB by showing stability of a microbunch structure over one turn in the storage ring. I will present the contributions made to this PoP experiment during a Master's thesis as well as the continuing efforts and perspectives of my PhD work in this project.

Speaker: Arnold Kruschinski (Helmholtz-Zentrum Berlin)

Kruschinski_SSMB_MT_Student_Retreat.pdf

7 HTS undulators: status and test results of prototype coils for compact FELs

Compact free electron lasers (FELs) require short period, high-field undulators in combination with shorter accelerator structures to produce coherent light up-to X-rays. Likewise, for the production of low emittance positron beams for future linear and circular lepton colliders, like CLIC or FCC-ee, high-field damping wigglers are required. Using high-temperature superconductors (HTS) in form of coated REBCO tape conductor allows for reaching higher magnetic fields and larger operating margins as compared to low-temperature superconductors, like Nb-Ti or Nb3Sn. This contribution discusses the development work done on two superconducting undulator geometries (vertical racetrack and helical) with a period length of 13 mm, as well as the status of the prototype coils. Measurement results from powering tests in LN2 of multiple vertical racetrack coils are presented, compared and discussed.

Speaker: Sebastian Richter (Karlsruhe Institute of Technology (KIT))

MTStudents_SCR_16-9_2022_KIT.pdf

8 Polarized Electron Beams from Laser Plasma Acceleration and Their Polarimetry

In recent years, Laser Plasma Acceleration (LPA) has become a promising alternative to
conventional RF accelerators. However, so far, it has only been theoretically shown that generating
polarized LPA beams is possible. The LEAP (Laser Electron Acceleration with Polarization)
project at DESY aims to demonstrate this experimentally for the first time, using a pre-polarized
plasma target.
The electron polarization will be measured with photon transmission polarimetry, which makes use
of the production of circularly polarized bremsstrahlung during the passage of the electron beams
through a suitable converter target. The photon polarization is then measured with the aid of
transmission asymmetry arising from reversing the magnetization direction of an iron absorber.
In this contribution an overview of the LEAP project is presented, detailing the generation of the
polarized electron beams along with the design and simulation studies of the polarimeter.

Speaker: Jennifer Popp (FTX (FTX Fachgruppe SLB))

JP_LEAP_MT2022.pdf

9 Compton Polarimetry in the hard x-ray regime

Photon polarization studies provide subtle information on the directionality and isotropy of the photon emission or interaction processes. As a lot of radiative processes provide distinct polarization features, the most rigorous experiments on these processes must also include a polarization analysis. Polarimetry in the hard x-ray regime can be performed by exploiting the polarization sensitivity of Compton scattering. For this purpose, within the Stored Particles Atomic Physics Research Collaboration (SPARC) several X-ray detectors based on large 2D sensitive semiconductor crystals were developed as dedicated Compton polarimeters. In this talk, I want to present the technique of Compton polarimetry using such a SPARC Compton polarimeter and show some results of a recent experiment on the polarization transfer in elastic scattering on an atomic target.

Speaker: Wilko Middents (HI Jena, FSU Jena)

MT2022_ComptonPolarimetry_Middents.pdf

12:15 Lunch break

Afternoon session

Convener: Gianpiero Vignola (ATLAS (ATLAS-Experiment))

10 What can go wrong?

Speaker: Ingrid-Maria Gregor (DESY/Uni Bonn)

MT_DESY_2022.pdf

11 X-Ray Spectroscopy of U90+ using Metallic Magnetic Calorimeters

Recent developments regarding metallic magnetic calorimeters (MMCs) have resulted in a new class of detectors for precision X-ray spectroscopy. One of them being the maXs series of detectors [1] (cryogenic microcalorimeter arrays for high resolution X-ray spectroscopy), which have been developed within the SPARC collaboration. They work as follows: The energy deposition of an incident X-ray photon leads to a measurable temperature rise of an absorber. At operation temperatures below 50 mK this leads to a change in the magnetisation of a paramagnetic sensor which can be measured by a superconducting quantum interference device (SQUID) [2]. MMC detectors combine a very high energy resolution (better than 100 eV FWHM at 100 keV) comparable to crystal spectrometers, with the broad bandwidth acceptance of semiconductor detectors (0.1 – 100 keV) [3].

These detectors are especially well suited for X-ray spectroscopy of highly charged ions. Helium-like ions, for example, are the simplest atomic multibody systems. Their study along the isoelectronic sequence provides a unique testing ground for the interplay of the effects of electron–electron correlation, relativity and quantum electrodynamics. However, for high-Z ions with nuclear charge Z > 54, where inner-shell transition energies reach up to 100 keV, there is currently no data available with high enough resolution and precision to challenge state-of-the-art theory [4]. We report on the first application of MMC detectors for high-resolution x-ray spectroscopy at the electron cooler of the low-energy storage ring CRYRING@ESR at GSI, Darmstadt. Within the presented experiment, the x-ray emission associated with radiative recombination of stored hydrogen-like uranium ions and cooler electrons was studied. Two maXs-100 detectors were placed at observation angles of 0° and 180° with respect to the ion beam axis. Special emphasis will be given to the achieved spectral resolution of better than 90 eV at x-ray energies close to 100 keV enabling for the first time to resolve the substructure of the K$_{α1}$ and K$_{α2}$ lines.

References

[1] C. Pies et al., J. Low Temp. Phys. 167, 269–279 (2012)
[2] D. Hengstler et al., Phys. Scr. 2015, 014054 (2015)
[3] S. Kempf et al., TDR maXs Cryogenic Micro-Calorimeter Arrays (2016): https://edms.cern.ch/ui/file/2059592/1/TDR_maXs_public_2016_02_11.pdf
[4] P. Beiersdorfer and G.V. Brown, Phys. Rev. A 91, 032514 (2015).

Speaker: Philip Pfaefflein (Helmholtz Institute Jena)

abstract_MTSR8_pfaefflein.pdf

MTSR8_talk_pfaefflein.pdf

12 Development of a Dual-Purpose Laser Teststand – HGCAL SiPM Quality Control and Saturation Analysis

For the approaching High-Luminosity-Upgrade of the Large Hadron Collider at CERN the development of the new detector systems will soon reach the production phase. This is also the case for the High Granularity Calorimeter (HGCAL), which will be applied in the endcaps of the Compact Muon Solenoid (CMS). The calorimeter uses silicon at the front and scintillators in the back, where the lower raditation level does allow it. It is specialized in the detection of showers of neutral hadrons. To increase the resolution of the detector systems the Particle Flow Algorithm (PFA) is to be utilized. On the hardware side this corresponds to the requirement of a highly granular calorimeter with over 200,000 individual scintillator tiles, where each light response is converted to an electrical signal by Silicon Photomultipliers (SiPMs). Besides the advantages of the PFA the high granularity also allows precise rejection of pile up events in the detector.

To guaranty high quality data and uniformity of the devices a fraction of the delivered SiPMs from Hamamatsu are to be tested for characteristics like the breakdown voltage, dark-count rate and gain. Besides the quality control, the behavior of the SiPMS at maximum illumination is to be investigated. Due to a recovery time in the range of tens of nanosecond after the detection of a first photon of one pixel of a SiPM, a second photon hitting this same pixel during the recovery time can not be detected. Therefore saturation will be reached for a high incident photon flux.

To analyze this behavior and also test SiPMs for high quality a laser test stand is under development. Two measurement modes are foreseen, one for quality assurance for large numbers of SiPMs, where the strong laser input is attenuated and split into 32 output optical fibers and a second, high intensity mode, where almost the full output is used in two channels to illuminate and saturate even the largest SiPMs with up to 40,000 pixel. As a read-out the ASIC "Kanäle für Ladungsauslese von SiPMs" (KLauS) is used.

A status of the described test stand development will be given as well as possible first test measurements.

Speaker: Timo Christian (FTX (FTX Fachgruppe DTA))

Mt_TC_teststand.pdf

13 A TES for ALPS II and further dark matter searches

Transition Edge Sensors (TES) are superconducting microcalorimeters that can be used for
single-photon detection at extremely low backgrounds. When they are within their supercon-
ducting transition region ($\sim80~$mK for the TES in this work) small temperature fluctuations -
like the energy deposited by single photons - lead to large variations in resistance. These varia-
tions can be measured using Superconducting Quantum Interference Devices (SQUIDs). This
exciting technology will be used as a single-photon detector for the upcoming ALPS II exper-
iment, a light-shining-through-walls experiment at DESY Hamburg, searching for Axion-Like
Particles (ALPs), which are possible Dark Matter (DM) candidates. At ALPS II the detector
needs to detect single photons with a wavelength of 1064 nm at a rate of $\sim10^{−5}~$Hz leading
to very stringent dark count requirements. Therefore, the main challenges in commissioning
a TES for ALPS II involve determining and increasing its detection efficiency and reducing
dark counts as well as backgrounds introduced by e.g. black-body radiation. Due to the very
low dark count rates in our setup, our TES system might be viable for direct DM searches at
sub-MeV masses using electron-scattering of DM in the superconducting material, as well.
In this talk, the commissioning of a TES for the ALPS II experiment will be discussed, followed
by an outlook on the possible application of TESs as detectors for direct DM searches.

Speaker: Christina Schwemmbauer (ALPS (ALPS _ Any Light Particle Search))

MT_Student_Schwemmbauer.pdf

14:45 Coffee break

Afternoon session

Convener: Max Vitz (Forschungszentrum Jülich, RWTH Aachen)

14 Introduction to the Helmholtz Juniors

Speaker: Jennifer Popp (FTX (FTX Fachgruppe SLB))

MT_HeJu_Intro.pdf

15 Detection and Reconstruction of High-Flux Electron Energy Spectra in the Strong-Field QED Regime with LUXE

Conventional QED, an incredibly accurate physical theory, breaks down and becomes divergent at extremely high energy scales, and also in the presence of an extremely intense external electromagnetic field. LUXE (LASER Und XFEL Experiment), an experiment in design and planning here in Hamburg, intends to collide a high-intensity LASER pulse with highly boosted electrons and photons, up to 17.5 GeV from the Eu.XFEL, creating assisted strong electric fields up to and greater than the Schwinger limit of ~1.32 × 10^18 Vm^-1.

This creates a non-negligible probability of non-linear Compton Scattering and Breit-Wheeler interactions, the latter of which represents a spontaneous boiling of the vacuum. The rates and kinematics of these interactions will be measured to high accuracy, with high-statistics runs for the first time at LUXE. Detection challenges of the results of these interactions include low-flux positron detection and tracking in a high-radiation environment, GeV-photon spectrometry, and high-flux, high-energy electron energy distribution reconstructions for a variety of spectral shapes and dynamic ranges.

A Scintillator Screen & Camera system is employed for the electron detection system, where scintillation light from the screen is measured by remote optical cameras, and magnetic deflection of the charged particles is used as magnetic spectrometer to reconstruct energy distributions of the electron flux.

The LUXE experiment and its goals are introduced, before the design, reconstruction methods and expected results for this Scintillation Screen & Camera detector and its consequences for LUXE are discussed.

Speaker: John Andrew Hallford (FLC (Forschung an Lepton Collidern))

JohnH_MTmeeting_studentretreat.pdf

16 Split Boot - True network-based booting on heterogeneous MPSoCs

In the context of the High-Luminosity (HL) upgrade of the LHC, many custom ATCA electronics boards are being designed containing heterogeneous system-on-chip (SoC) devices, more specifically the Xilinx Zynq UltraScale+ (ZUS+) family. While the application varies greatly, these devices are regularly used for performing board management tasks, making them a fundamental element in the correct operation of the board. The large number of hundreds of SoC devices planned for the HL upgrade in 2027 creates significant challenges in their firmware deployment, maintenance, and accessibility.

Even though U-Boot on ZUS+ devices supports network boot through the preboot execution environment (PXE), the standard ZUS+ boot process contains application-specific information at earlier boot steps, particularly within the first stage boot loader (FSBL). This prevents the initialization of several devices from a universal image.

Inspired by the PXE boot, a novel boot method tailored to the specific needs of the ZUS+ is proposed. All application-specific ZUS+ configuration is moved to a network storage and automatically fetched during the boot process. Initially, the ZUS+ loads a partial configuration file that is stored locally and does not contain any application-specific information. Afterwards, it retrieves and applies the complete device configuration from the network.

For seamless integration, the entire process is considered, from firmware and software development to binary distribution in a large-scale system. As a result, the proposal consists of a mechanism for applying the device configuration and a highly automated framework for creating the necessary files that integrates with the standard Xilinx development toolset workflow.

Speaker: Marvin Fuchs (KIT)

mt_student_retreat_2022_mfuchs.pdf

17 Optimizing Beamlines with Image-to-Image surrogates

Optimizing Beamlines with Image-to-Image surrogates (DMA)

Beamlines are complex parts of a synchrotron – they consist of many components with many changeable parameters. Thus they are hard to set up as well as hard to optimize. We tackle this issue by using global optimization methods using simulations. However, since these methods require millions of simulation evaluations for proper optimization, the simulations are too slow, and we replace these with fast neural networks, which we call surrogate models.

Speaker: David Meier (Helmholtz-Zentrum Berlin)

dmeier_im2im.pdf