Quadrupole Law and Steering Options in the Linac4 DTL

The Linac4 drift-tube linac (DTL) reference design has been modified to reduce the power consumption in tank 1 by adjusting the accelerating field and phase laws. In this note we investigate three options for the transverse focusing lattice, quadrupole law, and two options for beam steering. We use acceptance, sensitivity to alignment errors and the probabiity of beam loss as figures of merit for evaluating each option

RF Breakdown in Drift Tube Linacs

The highest RF electric field in drift-tube linacs (DTLs) often occurs on the face of the first drift tube. Typically this drift tube contains a quadrupole focusing magnet whose fringing fields penetrate the face of the drift tube parallel to the RF electric fields in the accelerating gap. It has been shown that the threshold for RF breakdown in RF cavities may be reduced in the presence of a static magnetic field. This note offers a “rule of thumb” for picking the maximum “safe” surface electric field in DTLs based on these measurements

A Program to Generate a Particle Distribution from Emittance Measurements

We have written a program to generate a particle distribution based on emittance measurements in x-x’ and y-y’. The accuracy of this program has been tested using real and constructed emittance measurements. Based on these tests, the distribution generated by the program can be used to accurately simulate the beam in multi-particle tracking codes, as an alternative to a Gaussian or uniform distribution

Beam loss control in the LINAC4 design

The Linac4 DTL reference design has been modified to reduce the power consumption in tank 1 by modifying the accelerating field and phase law. In addition we have adopted an FFDD focusing lattice throughout to minimize expected losses resulting from alignment errors. We have observed, however, that this design suffers from decreasing transverse acceptance and a sensitivity to misalignments that causes any expected beam loss to occcur at the high energy end of the DTL. In this note we investigate two solutions to increase the acceptance, decrease its sensitivity to misalignments and eliminate the potential for a beam-loss “bottleneck” at 50 MeV

Goals, Strategies and First Discoveries of AO327, the Arecibo All-Sky 327 MHz Drift Pulsar Survey

We report initial results from AO327, a drift survey for pulsars with the Arecibo telescope at 327 MHz. The first phase of AO327 will cover the sky at declinations of -1 to 28 degrees, excluding the region within 5 degrees of the Galactic plane, where high scattering and dispersion make low-frequency surveys sub-optimal. We record data from a 57 MHz bandwidth with 1024 channels and 125 us sampling time. The 60 s transit time through the AO327 beam means that the survey is sensitive to very tight relativistic binaries even with no acceleration searches. To date we have detected 44 known pulsars with periods ranging from 3 ms to 2.21 s and discovered 24 new pulsars. The new discoveries include three millisecond pulsars, three objects with periods of a few tens of milliseconds typical of young as well as mildly recycled pulsars, a nuller, and a rotating radio transient. Five of the new discoveries are in binary systems. The second phase of AO327 will cover the sky at declinations of 28 to 38 degrees. We compare the sensitivity and search volume of AO327 to the Green Bank North Celestial Cap survey and the GBT350 drift survey, both of which operate at 350 MHz.Comment: Accepted for publication in Ap

Is assertive community treatment coercive?

Background: Assertive community treatment (ACT) has become one of the cornerstones of care for people with serious mental illnesses. ACT is usually conceptualized as incorporating a multidisciplinary team approach, active and persistent attempts to engage clients, direct provision of comprehensive health and social care, and in-vivo and out-of-hours working. In addition, the service is ongoing, not time-limited, and has a low practitioner-to-client ratio (usually 1:10). However, ACT is not without its critics, many of them focused on the use of "coercive" techniques with ACT patients 12. At one end of the spectrum are those opponents of ACT who contend, "ACT is largely a euphemistic label for coercion." Despite substantial interest in the coercive aspects of ACT, no studies have focused specifically on understanding the phenomenology of the use and experience of leverage in ACT. Methods: Staff and patients of 4 ACT teams in Manhattan were recruited to participate in focus groups exploring their experiences with and opinions about the use of leverage in ACT. A total of 21 patients and 24 staff members participated with group size ranging from 10 to 12 members. Results: With only one exception, patients said uniformly that they did not believe that their ACT team was coercive or went too far in pressuring them to comply with treatment. ACT staff seemed more aware of the dangers of engaging in coercive behavior. Hence, they indicated a need to "keep each other in check." Conclusion: This preliminary series of focus groups with patients and staff members of ACT programs revealed little evidence from either set of participants of significant use of leverage or perceptions of coercion. Instead both patients and staff reported that supporting patients and building relationships with them were the preferred mechanisms for promoting treatment goals. This study suggests that ACT is not an intrinsically coercive model for the delivery of mental health services

Earnestly Finding the Fun in Fund Codes

Collections and acquisitions staff at Virginia Tech and The University of Alabama presented two very different models for structuring fund codes and discussed the benefits and difficulties inherent to each method. Both groups share their philosophy and approach for allocating appropriate fund codes for budgeting, reporting, and analytical purposes, and highlight important considerations to be made when creating a fund code structure