A plan for the development of superconducting Undulator prototypes for LCLS-II and future FELs

Undulators serve as the primary source of radiation for modern storage rings, and more recently for the advent of Free-Electron Lasers (FELs). The performance of future FELs can be greatly enhanced using the much higher magnetic fields of superconducting undulators (SCU) [1]. For example, the LCLS-II hard x-ray undulator can be shortened by up to 70 m using an SCU in place of a PMU (permanent magnet undulator), or its spectral performance can be critically improved when using a similar length. In addition, SCUs are expected to be orders of magnitude less sensitive to radiation dose; a major issue at LCLS-II with its 1-MHz electron bunch rate. We present a funded R&D collaboration between SLAC, ANL, and LBNL, which aims to demonstrate the viability of superconducting undulators for FELs by building, testing, measuring, and tuning two 1.5-m long planar SCU prototypes using two different technologies: NbTi at ANL and Nb Sn at LBNL. Our goal is to review and reassess the LCLS-II HXR baseline plans (PMU) in July of 2015, after the development and evaluation of both prototypes, possibly in favor of an SCU for LCLS-II.

Hadron Energy Reconstruction for the ATLAS Calorimetry in the Framework of the Non-parametrical Method

This paper discusses hadron energy reconstruction for the ATLAS barrel prototype combined calorimeter (consisting of a lead-liquid argon electromagnetic part and an iron-scintillator hadronic part) in the framework of the non-parametrical method. The non-parametrical method utilizes only the known $e/h$ ratios and the electron calibration constants and does not require the determination of any parameters by a minimization technique. Thus, this technique lends itself to an easy use in a first level trigger. The reconstructed mean values of the hadron energies are within $\pm 1$ of the true values and the fractional energy resolution is $[(58\pm3)/\sqrt{E}+(2.5\pm0.3)$. The value of the $e/h$ ratio obtained for the electromagnetic compartment of the combined calorimeter is $1.74\pm0.04$ and agrees with the prediction that $e/h > 1.7$ for this electromagnetic calorimeter. Results of a study of the longitudinal hadronic shower development are also presented. The data have been taken in the H8 beam line of the CERN SPS using pions of energies from 10 to 300 GeV.Comment: 33 pages, 13 figures, Will be published in NIM

Results from a combined test of an electromagnetic liquid argon calorimeter with a hadronic scintillating-tile calorimeter

The first combined test of an electromagnetic liquid argon accordion calorimeter and a hadronic scintillating-tile calorimeter was carried out at the CERN SPS. These devices are prototypes of the barrel calorimeter of the future ATLAS experiment at the LHC. The energy resolution of pions in the energy range from 20 to 300~GeV at an incident angle $\theta$ of about 11$^\circ$ is well-described by the expression \sigma/E = ((46.5 \pm 6.0)\%/\sqrt{E} +(1.2 \pm 0.3)\%) \oplus (3.2 \pm 0.4)~\mbox{GeV}/E. Shower profiles, shower leakage, and the angular resolution of hadronic showers were also studied

EFFECTS OF GEOMETRICAL ERRORS ON THE FIELD QUALITY IN A PLANAR SUPERCONDUCTING UNDULATOR

Short period superconducting undulators are being developed at the Advanced Photon Source APS . A 21 period undulator prototype is being fabricated. Later, the short coil will be replaced with a longer one using the same cryostat. A high quality magnetic field with a phase error of 2 degrees rms was achieved in the prototype magnets due to accurate winding of the superconducting coils on the precisely machined formers. Manufacturing meterslong undulator magnetic structures is a challenging task. A detailed understanding of the impact of geometric tolerances on the spectral performance is essential and appropriate manufacturing techniques have to be applied. The magnetic fingerprints of positioning errors of the superconducting windings in a planar structure are derived. Using these data the field profile of a long nonideal undulator magnet is then built and analyzed with respect to phase errors. The spectral performance degradation due to random and systematic geometric errors is presented. http accelconf.web.cern.ch AccelConf IPAC2012 papers moppp065.pd

Short Period Undulators for Storage Rings and Free Electron Lasers

Short period undulators have the potential to enhance the spectral performance of synchrotron radiation sources significantly. These devices open the range of brilliant hard Xrays at medium energy storage rings, their implementation may reduce the facility length of linac based FELs and they are an essential prerequisite for laser plasma accelerator based FELs. The development of cryogenic permanent magnet undulators has started and the first devices, employing period lengths around 18mm, have been installed in 3rd generation storage rings. Ambitious magnet designs permit even smaller period lengths which improve their performance further. The paper discusses the performance of cryogenic permanent magnet undulators in comparison with superconducting undulator