NEC SSAMS 加速器质谱

Single Stage Accelerator Mass Spectrometry (SSAMS)

单极加速器质谱

DESIGN 设计

The Single Stage Accelerator is based on an air insulated 250kV deck. This accelerator is the basis of a complete Accelerator Mass Spectrometry (AMS) System specially constructed to measure the amount of 14C in small graphite samples to a precision of 0.3% or better.

单极加速器基于250KV的空气绝缘板。这个在完整加速器质谱系统基础上，特制用于测量小石墨样品中的14C，精度可以达到0.3%或更好。

This system employs the fast, 10 Hz, sequential energy pulsing technique first used in the early 1980’s by the group at Eidgen?ssische Technische Hochschule, ETH, Zurich.

本系统采用的快速，10Hz，连续能量脉冲技术（首次应用在1980年代初由集团在eidgen?ssische工业学院，ETH，苏黎世）。

In this system a beam of C- ions is produced by bombarding the cool cesiated surface of a graphite sample with about 5 keV Cs+ ions.

在这个系统中，C-离子束是用大概5 keV Cs+离子来轰击石墨样品的铯表面而产生。

The C- beam produced by the sputtering of the sample by the Cs+ beam is accelerated, focused, and mass analyzed into mass 14, 13, and 12 amu beams.

C-离子的产生通过Cs+离子束溅射样品，C-离子被加速，聚焦，然后质谱分析器分离成14， 13， 12质量数。

These beams are then accelerated to about 275 keV in sequence by successively changing their energy as they pass through the mass analyzer so that they are on the correct trajectory for transmission into the Single Stage accelerator.

这些离子束然后通过275KeV加速，然后当他们通过质量分析器时改变能量，以使得他们以正确的轨迹传输到单级加速器。

The energy changing sequencer is adjusted about 10 times per second so that about 1 part in 105 of the mass 12 beam, 1 part in 103 of the mass 13 beam, and 99.8% of the

mass 14 beam passes into the accelerator keeping average accelerated and beam loading currents very low and X-rays produced directly or indirectly by high energy ions also very low.

能量变化的时序器调整大约每秒10次，以至于质量数12的离子束1/10⁵，质量数13的离子束的1/10³ ， 以及98%的离子束通过加速器并保证了平均的加速，并且离子束载入电流非常小，并且由于高能量离子束直接或间接产生的X射线会很小。

The beam of negative ions is 275 keV in energy when it reaches a region of relatively high gas pressure, the molecular ion dissociator canal, located on the high voltage deck. The fast moving negative ions lose electrons and become predominantly C+ ions when passing through the canal.

负离子束在能量是275keV，当达到相对高气体压力，分子离解通道，安装在高电压板。快速移动的负离子失去电子，变成主要的C+离子当通过通道时。

Also critical to the AMS process, negative molecular ions such as CH- and CH-2 are broken into C+n and H+ ions by the dissociator gas. This eliminates interferences that

might be caused by molecular ions when counting 14C+ ions later in the system.

对于AMS同样重要的是：负分子离子束比如CH- 和 CH-2 将转变成C+n和H+离子，当通过铯气体时。可能由分子离子产生的干扰的消除会在系统后。

The singly charged ions are magnetically deflected and focused at 90° by the analyzing magnet so that the pulses of 12C+ and 13C+ can be separated from

the 14C+ and measured in Faraday cages.

单电荷离子的磁偏转和聚焦在90°通过磁铁，C12+离子和C13+离子将会从C14+离子中分开，并由法拉第杯检测。

The 14C+  ions and a small number of 12C+ or 13C+ ions from the molecular breakup in the terminal that have exactly the right energy to be transmitted around the 90° magnet then pass into a 90° electrostatic spherical analyzer (ESA) which deflects the faster 12C+ and 13C+ ions away from the 14C+ ion beam  path.

14C离子和少量的12C +或13C +离子从分子的分裂在终端有正确的能量被传输的90°磁铁周围然后进入90°静电分析仪（ESA）将更快的12C +和13C离子远离14C离子光路。

The ESA also provides a final focusing so that the 14C+ ions are transmitted to a solid state detector where they are counted. By recording the 12C and 13C currents and 14C counts as known and unknown samples are sputtered, the amount of 14C present in

a sample is determined to high accuracy.

ESA也提供一个最终的聚焦，以使得C14+离子可以被传输到一个固定的检测器中（被离子计数）。通过记录C12和C13电流，C14计数（已知样品和未知样品飞溅出），样品C14数量测量保持了高的准确性。

With appropriate corrections for how the 14C came to be in the sample, the years of radioactive decay  and a chronological age can then be found.

随着对样品中C14适当的更正，放射性衰变的年和年龄都可以发现。

SSAMS

SPECIFICATIONS技术指标

Ratio of 14C/12C from measurements of three (3) “modern” graphite carbon samples with a precision of 0.3% or better, using known solid samples of unlimited size provided by the buyer.

使用由客户提供的已知不限制大小的样品，三次测量“现代”石墨碳的样品，C14/C12精度可达0.3%或者更好。

Ratio of 13C/12C currents from three (3) solid graphite samples of unlimited size 0.3% or better.

对于固体石墨样品，不限制尺寸三次测量13C/12C比值不超过0.3%。

Ratio of 14C/12C for three (3) dead graphite samples 2.5 x 10-15 or lower, using Alfa Aesar graphite supplied by NEC.

1. 40 sample or 134 samplecesium sputter source

  40样品或134样品铯溅射源

2. 90° injector magnet with insulated chamber for sequencial injection

90°注射磁铁与顺序注射隔离室

3. 250kV acceleration tube 

250kV加速管

4. 250kV insulated deck  250KV绝缘甲板

5. 90° analysis magnet with wide exit pole for abundant isotope measurement

90°分析磁铁，包括为大量测量的宽出口极

6. 90° electrostatic spherical analyzer

90°静电球形分析器

7. solid state particle detector for measuring 14C events

测量C14固体粒子探测器