Options for the second Bunch Compressor Chicane of the CLIC Main Beam Line

For the second bunch compressor chicane at CLIC a maximum emittance growth of only 5% in the horizontal plane is allowed. The emittance growth is the conse- quence of incoherent and coherent synchrotron radiation emitted by the electrons along the chicane. Both effects are reviewed and various chicanes are compared in computer simulations. A chicane layout is found which preserves the emittance well within the specifications

BCR::ABL1 levels at first month after TKI discontinuation predict subsequent maintenance of treatment-free remission: A study from the “GRUPPO TRIVENETO LMC”

We analyzed BCR::ABL1 expression at stop and in the first month after discontinuation in 168 chronic myeloid leukemia patients who stopped imatinib or 2nd generation tyrosine kinase inhibitors (2G-TKIs) while in sustained deep molecular response. Patients were divided among those who maintained response (group 1, n = 123) and those who lost major molecular response (group 2, n = 45). Mean BCR::ABL1 RNA levels 1 month after discontinuation were higher in group 2 than in group 1 (p = 0.0005) and the difference was more evident 2 months after stop (p < 0.0001). The same trend was found both for imatinib and 2G-TKIs. A receiver operating characteristic (ROC) analysis to determine a threshold value of BCR::ABL1 at 1 month after discontinuation identified a cut-off value of 0.0051%, with 92.2% specificity, 31.7% sensitivity and a likelihood ratio of 4.087

Isolated terawatt attosecond hard X-ray pulse generated from single current spike

Isolated terawatt (TW) attosecond (as) hard X-ray pulse is greatly desired for four-dimensional investigations of natural phenomena with picometer spatial and attosecond temporal resolutions. Since the demand for such sources is continuously increasing, the possibility of generating such pulse by a single current spike without the use of optical or electron delay units in an undulator line is addressed. The conditions of a current spike (width and height) and a modulation laser pulse (wavelength and power) is also discussed. We demonstrate that an isolated TW-level as a hard X-ray can be produced by a properly chosen single current spike in an electron bunch with simulation results. By using realistic specifications of an electron bunch of the Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL), we show that an isolated, &gt;1.0 TW and similar to 36 as X-ray pulse at 12.4 keV can be generated in an optimized-tapered undulator line. This result opens a new vista for current XFEL operation: the attosecond XFEL

Beam Current Measurements at the Nano-Ampere Level Using a Current Transformer

In conventional proton therapy (PT) typical beam currents are of the order of 0.1 nA. At these currents dose monitoring is reliably achieved with an ionization chamber. However, at the very high dose rates used in FLASH irradiations (employing beam currents &gt;100 nA) ionization chambers will exhibit large intensity dependent recombination effects and cannot be used. A possible solution is a current transformer. Here we report on the performance of the LC-CWCT (Bergoz Instrumentation, France) which has been developed to push noise floor of such non-destructive current measurement systems into the nano-ampere range. We present first beam current measurements at the PARTREC cyclotron (Netherlands). Beam currents measured by the LC-CWCT and a Faraday Cup were shown to linearly correlate up to the maximum intensity of 400 nA used in the measurements. For pulsed beams, charge measured by the LC-CWCT linearly correlated with pulse length over the measurement range from 50 to 1000 µs. Measurement noise as low as 2.8 nA was achieved. The results confirm that the LC-CWCT has the potential to be applied in FLASH PT for accurate determination of beam current and macro pulse charge.</p

Turn around loop and chicane for bunch compression and path length tuning in the CLIC drive beam

To achieve the proposed luminosity, phase and energy of the CLIC drive beam must meet tight specifications. The phase stability is achieved by a feedforward system consisting of two phase measurement stations intersected by a bunch compressor chicane in front of a turn around loop and a final chicane for bunch compression and path length correction behind the loop. This chicane is foreseen to compress the bunches to a final length of 0.4mm and should allow a path length tuning of 0.1mm. Suitable layouts for the turn around loop and the chicanes and results of beam dynamics simulations including incoherent and coherent synchrotron radiation are presented

A bunch compressor for the CLIC main beam

The last bunch compressor chicane in front of the main linac of the multi TeV linear collider CLIC is foreseen to longitudinally compress the incoming electron bunches from $σ_s$ = 250 μm to $σ_s$ = 30 μm. It is specified that the emittance growth in this chicane, which is mainly due to incoherent and coherent synchrotron radiation, should not exceed 30 nm rad in the horizontal plane and 1 nm rad in the vertical plane. To achieve these values the chicane layout and the optics functions have been optimized and the influence of shielding due to the vacuum chamber has been studied. The importance of the CSR micro bunch instability is discussed. Chicane layouts and the corresponding electron beam parameters are presented, which allow to preserve the emittance within the specifications

Designing a bunch compressor chicane for a multi-TeV linear collider

Incoherent and coherent synchrotron radiation are issues in most new accelerator projects utilizing bunch compressors to increase the peak current of the electron beam. Here we present a systematic approach to design a bunch compressor chicane suitable for the multi-TeV compact linear collider (CLIC). Based on analytical equations and beam dynamics simulations, we discuss how the influence of incoherent and coherent synchrotron radiation on the transverse beam emittance depends on chicane and electron beam parameters. The optimization of the bunch compressor layout and the electron beam parameters results in two different options which preserve the emittance to well within the specifications