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We report upon the performance of an analog hadron calorimeter prototype, where plastic scintillator tiles are read out with wavelength-shifting fibers coupled to avalanche photodiodes. This prototype configuration has been tested using a positron beam at DESY with energies between 1 and 6 GeV. We present different detector calibration methods, show measurements for noise, linearity, and energy resolution and discuss gain monitoring with an LED system. The results are in good agreement with our simulation studies and previous measurements using silicon photomultiplier readout.

Narrow X-ray lines from helium-like argon emitted from a dedicated ECR source have been used to determine the response function of a Bragg crystal spectrometer equipped with large area spherically bent silicon (111) or quartz (10$\bar{1}$) crystals. The measured spectra are compared with simulated ones created by a ray-tracing code based on the expected theoretical crystal's rocking curve and the geometry of the experimental set-up., Version acceptee (NIM)

Nuclear instruments & methods in physics research / A 538(1-3), 45 - 64 (2005). doi:10.1016/j.nima.2004.09.003, A systematic study is presented on the superconductivity (sc) parameters of the ultrapure niobium used for the fabrication of the nine-cell 1.3 GHz cavities for the linear collider project TESLA. Cylindrical Nb samples have been subjected to the same surface treatments that are applied to the TESLA cavities: buffered chemical polishing (BCP), electrolytic polishing (EP), low-temperature bakeout (LTB). The magnetization curves and the complex magnetic susceptibility have been measured over a wide range of temperatures and dc magnetic fields, and also for di erent frequencies of the applied ac magnetic field. The bulk superconductivity parameters such as the critical temperature Tc = 9.26 K and the upper critical field Bc2(0) = 410 mT are found to be in good agreement with previous data. Evidence for surface superconductivity at fields above Bc2 is found in all samples. The critical surface field exceeds the Ginzburg-Landau field Bc3 = 1.695Bc2 by about 10% in BCP-treated samples and increases even further if EP or LTB are applied. From the field dependence of the susceptibility and a power-law analysis of the complex ac conductivity and resistivity the existence of two different phases of surface superconductivity can be established which resemble the Meissner and Abrikosov phases in the bulk: (1) coherent surface superconductivity, allowing sc shielding currents flowing around the entire cylindrical sample, for external fields B in the range between Bc2 and Bcohc3, and (2) incoherent surface superconductivity with disconnected sc domains between Bcohc3 and Bc3. The coherent critical surface field separating the two phases is found to be Bcoh c3 = 0.81Bc3 for all samples. The exponents in the power law analysis are different for BCP and EP samples, pointing to different surface topologies., Published by North-Holland Publ. Co., Amsterdam

TESLA Reports 11 pp. (2004)., The proposed linear electron-positron collider TESLA is based on 1.3 GHz superconducting niobium cavities for particle acceleration. For a center-of-mass energy of 500 GeV an accelerating field of 23.4 MV/m is required which is reliably achieved with a niobium surface preparation by chemical etching. An upgrade of the collider to 800 GeV requires an improved cavity preparation technique. In this paper results are presented on single-cell cavities which demonstrate that fields of up to 40 MV/m are accessible by electrolytic polishing of the inner surface of the cavity.

17th IEEE Particle Accelerator Conference, PAC 97, Vancouver, USA, 12 May 1997 - 16 May 1997; 65 pp. (1997)., For the SB-Linear-Collider project (SBLC) at DESY a redesign of the damping ring has been performed, mainly in order to optimise the dynamic aperture. The lattice of the proposed damping ring has a DBA structure, similar to the 3rd generation light sources ESRF, APS and SPRING-8. The damping ring is build up with 6 superperiods. The straight sections between these periods are used for the injection,ejection and rf-cavities. In turn, each superperiod consists of 6 DBA cells. The straight sections of these cells are used for the installation of the wigglers, which are needed for the damping. With the installation of overall 150 m of wigglers (B$_0$ = 2 T and $\lambda_0$ = 0.2 m) the equilibrium emittances are $\epsilon_{x,0}$ = 6.5 $\centerdot$ 10$^{−10}$ m $\centerdot$ rad and $\epsilon_{y,0}$ = 1.3 $\centerdot$ 10$^{−11}$ m $\centerdot$ rad (the corresponding normalised emittances are : $\epsilon_{x,n}$ = 3.8 $\centerdot$ 10$^{−6}$ m $\centerdot$ rad and $\epsilon_{y,0}$ = 7:6 $\centerdot$ 10$^{−8}$ m$\centerdot$rad . The damping time results in $\tau_y$ $\leq$ 3.4 ms. The dynamic acceptance including misalignment and magnet errors is in the range of A$_x$ $\leq$ 72 mm $\centerdot$ mrad and A$_y$ $\leq$ 80 mm $\centerdot$ mrad.

The 2001 Particle Accelerator Conference, PAC2001, Chicago, USA, 18 Jun 2001 - 22 Jun 2001; 3096-3098 (2001)., The exact alignment of accelerator components is of crucial importance for the production of low emittance beams. Once a beam-line section is set up, a supplementary correction of misalignments implies the knowledge of its magnitude which is difficult to determine using conventional adjusting instruments. An excellent alternative to measure existing misalignments of accelerator components is to vary machine parameters and compare the behaviour of the beam with results obtained from a simulation. It is obvious that time consuming particle tracking programmes are notappropriate to reach this aim. Regarding computing time, the on-line simulation code V is advantageous compared to other beam dynamics programmes. The theoretical basis of V-Code, the “Ensemble Model”, consists of selfconsistent equations for the ensemble parameters that arederived from the Vlasov equation. The requirement to simulate misalignments such as offsets and tilts led to the development of the ALIGNMENT UTILITY which utilizes the solver of V-Code. The new utility enabled us to investigate the beam-line alignment of the TESLA Test Facility injector.This contribution presents the theoretical background and an illustrating example of the optimization process.

The 2001 Particle Accelerator Conference, PAC2001, Chicago, USA, 18 Jun 2001 - 22 Jun 2001; 3771-3773 (2001)., This paper reports on recent beam measurements of higher order modes in the TESLA Test Facility (TTF) accelerating modules. Using bunch trains of about 0.5 ms with 54MHz bunch repetition and up to 90% modulated intensity, transverse higher order modes are resonantly excited when the beam is offset and their frequency on resonance with the modulation frequency. With this method, the trapped modes can be excited and their counteraction on the beam observed on a wide-band BPM downstream of the module. Scanning the modulation frequency from 0 to 27MHz allows a systematic investigation of all possible dangerous modes in the modules.

The 2001 Particle Accelerator Conference, PAC2001, Chicago, USA, 18 Jun 2001 - 22 Jun 2001; 2722-2724 (2001)., The TESLA linear collider incorporates an X-ray SASE FEL which demands challenging electron beam parameters (typically transverse emittance of 1.6 mm-mrd and peak current of 5 kA). For a realistic electron beam distribution at the entrance of the undulator, tracking has to be done from the cathode through the whole accelerator. Non-Gaussian beam profiles have to be taken into account as well as nonlinear effects such as space-charge, coherent synchrotron radiation field and wake fields. We have done this with several codes: Astra, for the low energy part (

539469 5 pp. (2001)., By running the prospective high-energy $e^+e^−$ collider TESLA in the GigaZ mode on the $Z$ resonance, experiments can be performed on the basis of more than 109 $Z$ events. This will allow the measurement of the effective electroweak mixing angle to an accuracy of $\delta \sin^2 θ_{\mathrm{eff}}≈±1×10^{−5}$. The $W$ boson mass is likewise expected to be measurable with an error of $\delta M_W≈±6$ MeV near the $W^+W^−$ threshold. We review the electroweak precision tests that can be performed with these high precision measurements within the Standard Model (SM) and its minimal Supersymmetric extension (MSSM). The complementarity of direct measurements at a prospective linear $e^+e^−$ collider and indirect constraints following from the measurements performed at GigaZ is emphasized.

TESLA Reports 2003 9 pp. (2003)., The paper contains the analysis of the application possibilities offered by the new generation of the FPGA chips. The new generation of the FPGA chips contain DSP blocks. The new functionalities are well suited for the application in the TESLA LLRF cavity simulation and control system (SIMCON). A debate on the programming methods of the new chips and the algorithm parameterization was presented. The aim of the, FPGA chip based, system analysis is the optimal chip usage to increase the maximum frequency at which the system can work efficiently, and the optimal usage of the accessible chip resources (DSP blocks). The exemplary results for a few practical calculated implementations were presented and analyzed. The implementations included some basic DSP operations performed in the FPGA chips of Altera and Xilinx. There were compared the results for a few different chips. The TESLA superconducting cavity simulator was efficiently implemented. The results were presented for the first time, for the pure FPGA/VHDL solution. The realization costs were debated in the dependence of given system parameters and the applied type of the FPGA chip.

TESLA Reports 2003 9 pp. (2003)., The pioneering TESLA linear accelerator and free electron laser project is initially introduced. Elementary analysis of cavity resonator with signal and power considerations is presented. Two alternative simulation models of cavity control system are proposed.

TESLA Reports 2003 8 pp. (2003)., This paper presents a new FPGA based solution of the Low Level RF Control System for the TESLA Test Facility. The LLRF Control System is responsible for maintaining the constant amplitude and phase of accelerating field in the cavities in the accelerator’s cryomodules driven by single klystron (up to 32 cavities). To obtain shorter processing time and less complicated hardware an FPGA based solution was selected. The proposed simulation has been simulated in software, and appeared to be faster and less complex than DSP based solutions.

The cavity control system for the TESLA - TeV–Energy Superconducting Linear Accelerator project is initially introduced. The elementary analysis of the cavity resonator on RF (radio frequency) level and low level frequency with signal and power considerations is presented. For the field vector detection the digital signal processing is proposed. The electromechanical model concerning Lorentz force detuning is applied for analyzing the basic features of the system performance. For multiple cavities driven by one klystron the field vector sum control is considered. Simulink model implementation is developed to explore the feedback and feed-forward system operation and some experimental results for signals and power considerations are presented.

The 2001 Particle Accelerator Conference, PAC2001, Chicago, USA, 18 Jun 2001 - 22 Jun 2001; 286-288 (2001)., At DESY the Distributed Object Oriented Control System (DOOCS)[1] was developed to solve a variety of control tasks at the TESLA Test Facility (TTF) Linac. DOOCS is designed from the device server level, to control different parts of the hardware, up to the console, where it provides a graphical user interface (GUI) to the operators. The Finite State Machine (FSM) concept has been integrated into DOOCS to simplify the automation of the accelerator operation[2, 3]. This paper describes the FSM server implementation for automated RF operation at the TTF. The server consists of two main elements – the control manager and a tools section. The control manager is responsible for RF field control. The start up, restart and routine operation of a 10MW klystron, that currently powers 16 superconducting cavities, is successfully controlled by a DOOCS FSM server. The FSM process includes loop phase measurement and correction, feedforward and feedback parameter adjustments, beam loading compensation, calibrations, and automatic fault recovery. A variety of automated procedures are available in the tools section, which assist the operators in maximizing the performance of the RF system.

16 pp. (2001)., The TESLA detector asks for a strong and very homogeneous magnetic field within its useful volume. In this respect, a large superconducting magnet has been designed, with special attention to get the requested field homogeneity. The design of the magnet, a superconducting solenoid with its iron yoke, is described in this paper, with some emphasis on the achievement of the field homogeneity.

TESLA Reports 2003 9 pp. (2003)., This paper describes an alternative approach for control and data acquisition system to be used in TESLA controller and simulator (SIMCON) boards [1]. The standard VME controller may be replaced with a cheap embedded PC to provide equivalent or even superior functionality. The new approach offers better cost/performance ratio, better scalability of the system and better testability of the SIMCON boards.

The 2001 Particle Accelerator Conference, PAC2001, Chicago, USA, 18 Jun 2001 - 22 Jun 2001; 86-88 (2001)., The TTF Free Electron Laser requires high current electron bunches with small emittances. The beam is produced by an injector based on a laser driven rf gun. The design aims for a bunch charge of 1 nC, a bunch length in the mm range, and a normalized transverse emittance approaching1mm mrad. Emittance measurements in the photoinjector after preacceleration to 17MeV are presented and compared to simulations.

The 7th European Particle Accelerator Conference EPAC 2000, EPAC 2000, Vienna, Austria, 26 Jun 2000 - 30 Jun 2000; Hamburg : DESY 1803-1805 (2000)., The design, construction and first tests of a prototype of the beam trajectory monitor at the TTF-FEL are presented. With this monitor the off-axis spontaneous undulator radiation is imaged through a set of pinholes onto silicon pixel detectors. This allows to measure simultaneously 12 points of the transverse beam position with an accuracy of better than 10 $\mu$m over a length of 5 m. The prototype consists of a pinhole mask and the pixel detectors accurately placed to each other inside a vacuum chamber which is held under beam vacuum. We first present the design and the production technology of the silicon pixel detector. Then the optimization of the pinhole mask and its realization using lithographic methods are discussed. To determine its spatial accuracy the detector is scanned using a laser test stand and a low-intensity electron beam of an electron microscope. The symmetry axis of the detector defines a straight line within 0.4 $\mu$m. Additionally, the electron microscope is used to study the radiation hardness of the detector. The sensitivity of the detector to low energy X-rays is measured using a vacuum ultraviolet beam at the synchrotron light source HASYLAB. Finally first calibration measurementsof the BTM prototype detectors are shown., Published by DESY, Hamburg

TESLA Reports 2003 9 pp. (2003)., The paper describes a functional idea of the parameterized control layer for the FPGA based advanced electronic and photonic systems. The systems under considerations are used (or planned to be used) for the construction of distributed, control, simulation, measurement and data acquisition in the Low Level Radio Frequency (LLRF) part of the TESLA and X-Ray FEL projects in DESY. Practical realization of the control layer was presented. The implementation was done in FPGA Xilinx VirtexII V3000 chip embedded in XtremeDSP Development Kit board by Nallatech. The designed and implemented communications protocol was described. The protocol is based on the standard parallel EPP transmission from the PC.

The 2001 Particle Accelerator Conference, PAC2001, Chicago, USA, 18 Jun 2001 - 22 Jun 2001; 1342-1344 (2001)., At several locations of the beam delivery system (BDS) of a future linear collider (FLC), beam spot sizes ranging from several hundreds to a few micrometers have to be measured. It is anticipated that laser wires will be used for this task in any FLC design. In order to optimize a laser wire system, simulations and background measurements have been carried out. Results are presented from simulations of the Compton scattering for the PETRA scenario. Furthermore results from measurements of backgrounds like synchrotron radiation and gas scattering have been measured at the positron storage ring PETRA at DESY and will be discussed.

2 pp. (1999).