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A. S. Carroll, D. Dayton, E. Schwaner

--specification summary table-- postscript or gif
--Flux-- postscript
or gif

I. Introduction

The AGS B2 test beam is a general purpose beam for testing and developing particle detectors for use at the AGS and other accelerators, or for other applications such as space research. Occasionally very modest experiments can be performed if little or no support is required from the AGS Department, and special approval is obtained from the Laboratory Management. The arrangements are made as flexible and informal as possible to allow easy access by experimenters

II. Description

As shown in Fig. 1, particles for the B2 test beam are derived from 6 Deg production at the B primary target. This target can be a 2.5 cm long, 0.6 x 0.6 cm**2 Beryllium rod or 2mm thick Aluminum oxide flag.

The maximum fields of the the two dipoles set an upper limit to the beam momentum of 9 GeV/c. The magnets may be set as low 0.3 GeV/c, but the beam size increases decreasing momentum below about 1 GeV/c.

The calculated beam RMS size at 250 inches from the last quadrupole is 7mm(H) by 2mm(V). Their maximum full widths are 35mm(H) by 5mm(V).

III. Magnet Settings

The 2 dipoles, 4 quadrupoles, and 2 collimators of the B2 beam line are controlled through the "DIBBUK II" control system. This system based on Apollo/HP workstations is easily used. There are help files and a manual. The workstation will have a number of labeled files for different momenta and distances along the beam line. To reverse magnet polarities, page the "target desk" through main control( Ext 4662). Help for any problems connected with operating the DIBBUK II system or with the magnets or collimators themselves may be obtained through the "target desk".

The beam is tuned by selecting a DIBBUK file which is at or near the the momentum desired, and set for about the correct distance. There is a small table of values in Appendix I, and a number of charts near the DIBBUK terminal. Then B2D2 is adjusted in small (2Amp) steps to center the beam Page 2 on the apparatus. The momentum spread of the beam is set by B2C2(9mm per %). The vertical collimator B2C1 is then set to give the desired intensity. At the beginning of the tuning the collimators should be given moderate settings (+/-5mm horiz and +/-10mm vertically) to provide an adequate flux but not trip the radiation monitors.

IV. Particle Fluxes

The approximate particle fluxes for the beam line are shown in Fig 2. The curves indicate that radiation safety limit the overall flux in the beam to about 2 x 10**5 particles per spill. The fraction of electrons is about 1 to 2% at about 1 GeV/c and drops off to about 0.1 to 0.2% at 5 GeV/c. During 1994 a 2mm thick Pb converter[5cm(v)x2.5cm(h)] was inserted 50 cm downstream of the B target. This greatly enhanced the electron fraction. About 30% at 1 GeV/c and a few percent at 5 GeV/c. This converter can be rotated out the beam, but requires a primary cave access.

V. Experimental Safety

All equipment brought into the test beam must be considered from a safety point of view. The common safety items are the strength of mechanical supports, pressure vessels, flammable gases, and exposed high voltages. Table 2 provides a list of items which may need to be reviewed. See the Liaison Engineer if there are any questions.

VI. Test Beam Set Ups

The tests in the B2 line are generally set up in a serial fashion along the beam line. Since many of the tests are quite sensitive to material upstream of their detector, it is essential that each group be able to quickly and completely remove all material from the beam line when required.

There are about 3 meters of space on either side of the beam line.

VII. Common Beam Signals

The PHENIX group has set two beam scintillators and two threshold counters for use by anyone in the B2 line. Both analog and discriminated signals are available at the upstream end of the beam line.

The C1 Cerenkov counter can be pressurized up to 40 psi. The C2 counter is an atmospheric counter used for identifying electrons.

VIII. Lift tables

There are both manually operated lift tables ("Green Tables" - see Fig. 2), and remotely controlled x-y tables. See Liaison Engineer for details.

VI. Radiation Safety

Appendix III gives the present access procedures to the B2 beam. These procedures will be modified from time to time. In order to sweep and lock the area, users must undergo a brief training and walk through of the sweep procedures. These procedures must be followed very carefully because of the multiple users in the beam line. Any significant violation of the rules could result in serious radiation exposure and shut down of the B2 beam line and even the AGS accelerator.

In order to work on the AGS floor, users must have Radiation Workers Training and AGS Users Training. This training is extensive, so allow time for it. Users here for short periods of time can work on the AGS floor with a Red film badge provided they are escorted by a trained person.


In case of emergency such as fire, explosion or personal injury pull the nearest fire alarm box located near an exit door.

If you are not in danger, call AGS Main control - Ext 4662.

If the AGS is not operating, call Lab Security - Ext 2222.

X. Contacts

We have to deal with a large number of requests, and are not often in our offices. E-mail is the best method unless the request is very urgent.

Ed Schwaner, Liaison Engineer 516/344-4846 or page 3456-0732 (voice) E-mail: SCHWANER@BNLDAG.AGS.BNL.GOV

Alan Carroll, Liaison Physicist 516/282-4714 or page 3456-4218-ext (silent) E-mail: CARROLL@BNLDAG.AGS.BNL.GOV

Elaine Zukowski, AGS Users Secretary - Housing, Lab ID, etc 516/282-3866 E-Mail: HENP@BNL.GOV

Fig 1. Rough Schematic of B2 test beam

Beam direction ======>>>

T--------QV-----D1---QH-VC----HC-----QH----D2--C1--QV----C2-----{ }----BS

<----10 meters---->

T - Production Target - 6 Deg production
QV - Vertically focusing quad
D1,D2 - Dipoles: bend 8 Deg.
QH - Horizontally focusing quad
VC - Vertical Collimator - intensity control
HC - Horizontal Collimator - momentum bite - intermediate focus
C1,C2 Gas threshold Cerenkovs
BS - Beam stop More details available on request

Fig 2. - Flux

Number of particles per pulse in units of 10**6 in the B2 line for 0.25 x10**12 interacting as limited by Radiation Safety Requirements. Approximate beam size is 3 x 1.0 cm**2 - to be published

Percentage of positive particles (e,mu,pi,K,p) for B2 momentum settings from 0.3 to 9 GeV/c -- postscript or gif

Fig 3. AGS "Green Table" Specifications

table capacity............ 5000 lbs
top plate width ............ 26"
top plate length ........... 38"
over-all width ............. 30"
over-all length ............ 39"
minimum height ...........28"
maximum height .......... 42"

Appendix I (to be published)

Table of magnet settings at 1, 5 and 9 GeV/c

Appendix II (to be published)

List of items subject to safety review

Appendix III (to be published)

B2 Access procedures